• What do these three sets have in common?

    From James Dow Allen@user4353@newsgrouper.org.invalid to rec.puzzles on Sat Feb 21 17:18:17 2026
    From Newsgroup: rec.puzzles


    I'm thinking of three sets (of bit-strings) which are conceptually infinite. Each of the sets is in practical use and has a name.
    Here are the first twelve elements of each set:

    (A)
    1
    000
    010
    00100
    00110
    01100
    01110
    0010100
    0010110
    0011100
    0011110
    0110100

    (B)
    11
    011
    0011
    1011
    00011
    10011
    01011
    000011
    100011
    010011
    001011
    101011

    (C)
    00
    01
    100
    101
    1100
    1101
    11100
    11101
    111100
    111101
    1111100
    1111101

    Each of the infinite sets has the same special and useful property.
    __ What is that property? __
    Please rot13 any solution.

    Dearest regards. James Dow Allen (mail address: jamesdowallen at gmail)
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  • From HenHanna@NewsGrouper@user4055@newsgrouper.org.invalid to rec.puzzles,rec.games.trivia on Sat Feb 21 21:46:15 2026
    From Newsgroup: rec.puzzles



    great problem!!!


    James Dow Allen <user4353@newsgrouper.org.invalid> posted:


    I'm thinking of three sets (of bit-strings) which are conceptually infinite. Each of the sets is in practical use and has a name.
    Here are the first twelve elements of each set:

    (A)
    1
    000
    010
    00100
    00110
    01100
    01110
    0010100
    0010110
    0011100
    0011110
    0110100

    (B)
    11
    011
    0011
    1011
    00011
    10011
    01011
    000011
    100011
    010011
    001011
    101011

    (C)
    00
    01
    100
    101
    1100
    1101
    11100
    11101
    111100
    111101
    1111100
    1111101

    Each of the infinite sets has the same special and useful property.
    __ What is that property? __
    Please rot13 any solution.

    Dearest regards. James Dow Allen (mail address: jamesdowallen at gmail)
    --- Synchronet 3.21b-Linux NewsLink 1.2
  • From James Dow Allen@user4353@newsgrouper.org.invalid to rec.puzzles on Mon Feb 23 08:26:07 2026
    From Newsgroup: rec.puzzles


    James Dow Allen <user4353@newsgrouper.org.invalid> posted:


    I'm thinking of three sets (of bit-strings) which are conceptually infinite. Each of the sets is in practical use and has a name.
    Here are the first twelve elements of each set:

    (A)
    1
    000
    010
    00100
    00110
    01100
    01110
    0010100
    0010110
    0011100
    0011110
    0110100

    (B)
    11
    011
    0011
    1011
    00011
    10011
    01011
    000011
    100011
    010011
    001011
    101011

    (C)
    00
    01
    100
    101
    1100
    1101
    11100
    11101
    111100
    111101
    1111100
    1111101

    Each of the infinite sets has the same special and useful property.
    __ What is that property? __
    Please rot13 any solution.


    As a hint, I'll provide another puzzle! This puzzle isn't really related
    to the prior puzzle ("What special property do sets A, B and C have?"
    although it implies a finite set with the same property) BUT it is a
    puzzle in the SAME DOMAIN as the original puzzle.
    Guess the relevant domain and both puzzles may fall into place.

    As the hint/puzzle I define a transformation and then post a comment and
    a challenge question about that transformation:

    Transformation:
    00 rRR 1
    01 rRR 01
    1 rRR 00

    Comment: This .......... .... is essentially ....... over a binary ........ when the ........... .. . is a stationary 29%.

    Question: What special property does this .......... .... have
    which is quite rare among optimal .......... .....?


    -----------------------
    Dearest regards. James Dow Allen (mail address: jamesdowallen at gmail)
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  • From James Dow Allen@user4353@newsgrouper.org.invalid to rec.puzzles on Thu Feb 26 10:41:28 2026
    From Newsgroup: rec.puzzles


    James Dow Allen <user4353@newsgrouper.org.invalid> posted:
    James Dow Allen <user4353@newsgrouper.org.invalid> posted:


    I'm thinking of three sets (of bit-strings) which are conceptually infinite.
    ...
    Each of the infinite sets has the same special and useful property.
    __ What is that property? __

    As a hint, I'll provide another puzzle! ... a
    puzzle in the SAME DOMAIN as the original puzzle.
    Guess the relevant domain and both puzzles may fall into place.

    Transformation:
    00 rRR 1
    01 rRR 01
    1 rRR 00

    Comment: This .......... .... is essentially ....... over a binary ........ when the ........... .. . is a stationary 29%.

    Question: What special property does this .......... .... have
    which is quite rare among optimal .......... .....?

    Apparently my puzzles were either too difficult or too boring.
    Please post a reply, however brief, if you even read the puzzles.

    Cheers,
    James
    --- Synchronet 3.21b-Linux NewsLink 1.2
  • From David Entwistle@qnivq.ragjvfgyr@ogvagrearg.pbz to rec.puzzles on Thu Feb 26 12:26:35 2026
    From Newsgroup: rec.puzzles

    On Thu, 26 Feb 2026 10:41:28 GMT, James Dow Allen wrote:

    Apparently my puzzles were either too difficult or too boring. Please
    post a reply, however brief, if you even read the puzzles.

    Hi James,

    No, not boring - quite interesting.

    Initially I was thinking of layers of bricks on a apex roof line - long
    and short side on - Flemish-bond like. Not that, although I have been
    thinking about a question related to the angle of an apex roof based on standard brick sizes and arrangements...

    With the additional clue - I was thinking some sort of dither, or
    something along the lines of NRZ coding, which I've come across in my
    previous life. I don't think it's anything to do with that though. In some cases previous experience directs your thoughts and can be a hindrance to
    more creative thought.

    I think you've laid out what it is, but I can't see the exact algorithm,
    or protocol to be applied. Somethings you see and something you don't. In
    some ways, the things you don't see are more interesting than the things
    you do, as you learn something new.

    Best wishes,
    --
    David Entwistle
    --- Synchronet 3.21b-Linux NewsLink 1.2
  • From Matt@us@gather.info to rec.puzzles on Thu Feb 26 15:57:43 2026
    From Newsgroup: rec.puzzles

    On Thu, 26 Feb 2026 10:41:28 GMT, James Dow Allen wrote:

    Apparently my puzzles were either too difficult or too boring. Please
    post a reply, however brief, if you even read the puzzles.

    Cheers,
    James

    Am here, reading and enjoying the puzzling. Thank you and please keep 'em coming :)

    - Matt
    --- Synchronet 3.21b-Linux NewsLink 1.2
  • From James Dow Allen@user4353@newsgrouper.org.invalid to rec.puzzles on Thu Feb 26 20:09:53 2026
    From Newsgroup: rec.puzzles


    James Dow Allen <user4353@newsgrouper.org.invalid> posted:
    James Dow Allen <user4353@newsgrouper.org.invalid> posted:


    I'm thinking of three sets (of bit-strings) which are conceptually infinite.
    Each of the sets is in practical use and has a name.

    I don't want to just blurt out the answer. So I'll show some nice
    properties that the sets have:

    Here are the first twelve elements of each set:

    The elements of (A) have lengths 1,3,3,5,5,5,5,7,7,7,7,7,... respectively.
    If the bits are 50-50 coin tosses, then from a given starting point
    '000' will occur with probability 1/8; and so on.
    (A)
    1 --> 1 ... 1/2
    000 --> 3 ... 1/8
    010 --> 3 ... 1/8 (or 1/2^3)
    00100 \
    00110 \
    01100 / --> 5,5,5,5 ... 4/32 (or 4/2^5)
    01110 /
    0010100 \
    0010110 \
    0011100 / --> 7,7,7,7,7 ... 5/128 (or 5/2^7)
    0011110 /
    0110100 /

    1/2 + 1/8 + 1/8 + 4/32 + 5/128 = 0.914
    But these are INFINITE sets. If we continue, get
    1/2 + 1/8 + 1/8 + 4/32 + 8/128 + 16/512 + 32/2048 + 64/8192 +... = 0.992 Asymptotic to 1. This is a necessary but insufficient condition for sets
    with all the special properties.

    Repeat this for set (B) and get
    1/4 + 1/8 + 2/16 + 3/32 + 5/64 + 8/128 + 13/256 + 21/512 + 34/1024
    + 55/2048 + 89/4096 + 144/8192 + 233/16384 + 377/32768 = 0.951 ...
    Also converging to 1, but very slowly.
    By the way, dig those numerators?! There are 1, 1, 2, 3, 5, 8 tokens
    of length 2, 3, 4, 5, 6, 7, respectively.

    Another nifty feature of set (B) is that it is a place-value representation (with an extra 1 appended) of the natural numbers:

    (B)
    ... 12358
    11 = 1 (always ignore the terminal 1; it is used as a "comma.")
    011 = 2
    0011 = 3
    1011 = 1+3
    00011 = 5
    10011 = 1+5
    01011 = 2+5
    000011 = 8
    100011 = 1+8
    010011 = 2+8
    001011 = 3+8
    101011 = 1+3+8
    ... 12358

    Every element of set (B) terminates with '11' but never has other
    instances of '11' inside.

    A typical computer program would spend 8 bits (00000011) to represent
    the very small integer 3. And would be unable to represent any
    integer larger than 255 (11111111).
    But (B) uses only 4 bits (0011) to represent 3. And there is no limit
    to the size of integers which can be represented.
    In what application domain would this be useful?

    (C) is also a simple rendering of the natural numbers
    (though now 0 is included).
    (C)
    00 = 0
    01 = 1
    100 = 2+0
    101 = 2+1
    1100 = 2+2+0
    1101 = 2+2+1
    11100 = 2+2+2+0
    11101 = 2+2+2+1
    111100 = 2+2+2+2+0
    111101 = 2+2+2+2+1
    1111100 = 2+2+2+2+2+0
    1111101 = 2+2+2+2+2+1

    Each of the infinite sets has the same special and useful property.
    __ What is that property? __

    The way that '11' serves as a terminator in (B) above may offer a hint
    to the solution of this puzzle.

    Cheers,
    James
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  • From Mike Terry@news.dead.person.stones@darjeeling.plus.com to rec.puzzles on Thu Feb 26 21:24:05 2026
    From Newsgroup: rec.puzzles

    On 26/02/2026 10:41, James Dow Allen wrote:

    James Dow Allen <user4353@newsgrouper.org.invalid> posted:
    James Dow Allen <user4353@newsgrouper.org.invalid> posted:


    I'm thinking of three sets (of bit-strings) which are conceptually infinite.
    ...
    Each of the infinite sets has the same special and useful property.
    __ What is that property? __

    As a hint, I'll provide another puzzle! ... a
    puzzle in the SAME DOMAIN as the original puzzle.
    Guess the relevant domain and both puzzles may fall into place.

    Transformation:
    00 rRR 1
    01 rRR 01
    1 rRR 00

    Comment: This .......... .... is essentially ....... over a binary ........ >> when the ........... .. . is a stationary 29%.

    Question: What special property does this .......... .... have
    which is quite rare among optimal .......... .....?

    Apparently my puzzles were either too difficult or too boring.
    Please post a reply, however brief, if you even read the puzzles.

    Cheers,
    James

    Not boring at all, but... I don't always see an answer, especially a full answer, and time is
    limited!...

    So looking at your original post, I see some properties, but don't really have a full answer!

    The sequences remind me of Huffman codes, and Huffman codes wouldn't work if sequences of them
    couldn't be uniquely interpreted. Your sets have this property, so we could say they're like an
    infinite set of Huffman codes(?).

    Worded differently, all your sets seem to have the property that no two strings start with the same
    prefix. We could interpret them as finite nodes in an infinite binary tree, and each of these nodes
    has the property that its path does not pass through any other nodes.

    Also, it seems the sets of nodes are constructed (more or less) by some kind of fractal pattern.
    E.g. set A seems to have a generator pattern (apart from the entry 1):

    A
    / \
    / \
    x x
    / \ / \
    N A N A

    where we paste the root A where it occurs below. The Ns are the terminal nodes, which are the ones
    in your set A, which appears to be listed in order depth then left-to-right. (Left being
    represented as 0, Right as 1).

    I'd guess the sets might be related to compression of infinite stream data??? Perhaps used somehow
    in video codecs? but I don't see exactly how, or know what their names would be.

    Other observations: For all the sets there are infinite paths that have no prefix in the set. Set
    A has uncountably many of these, e.g. 0010101010101... or 0111101011101... (basically, as long as
    odd-numbered digits (other than the first) are 1). All the sets have "enough" nodes so that a
    random path hits a node "almost certainly" (i.e. with probability 1). I don't know if that is
    important.

    But no end of other sets have these same properties - even if the "fractal" property is key. (I
    suppose that might be important when processing an infinite stream, because only a finite amount of
    context data would have to be maintained.


    Regards,
    Mike.

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  • From James Dow Allen@user4353@newsgrouper.org.invalid to rec.puzzles on Fri Feb 27 06:25:04 2026
    From Newsgroup: rec.puzzles


    (In my most recent post I suggested by example that the "Krafft sum"
    was asymptotically one, where each token in the set contributes 2^(-k)
    to the Krafft sum where k is the number of bits in that token.)


    Mike Terry <news.dead.person.stones@darjeeling.plus.com> posted:

    On 26/02/2026 10:41, James Dow Allen wrote:
    James Dow Allen <user4353@newsgrouper.org.invalid> posted:
    James Dow Allen <user4353@newsgrouper.org.invalid> posted:

    I'm thinking of three sets (of bit-strings) which are conceptually infinite.
    ...
    Each of the infinite sets has the same special and useful property.
    __ What is that property? __


    Not boring at all, but... I don't always see an answer, especially a full answer, and time is
    limited!...

    So looking at your original post, I see some properties, but don't really have a full answer!

    The sequences remind me of Huffman codes, and Huffman codes wouldn't work if sequences of them
    couldn't be uniquely interpreted. Your sets have this property, so we could say they're like an
    infinite set of Huffman codes(?).

    Kudos to Mike Terry! These are exactly like Huffman codes; a more general
    term is compaction codes. In a finite world, no token will actually be infinite but it is convenient to define mappings of the integers which are unbounded.

    A "Huffman code" is a compaction code which is optimal for some particular probability mass function. But EVERY compaction code with Krafft sum of one will be optimal for SOME distribution.

    Worded differently, all your sets seem to have the property that no two strings start with the same
    prefix.

    Yes. These are called "prefix codes" or "prefix-free codes" or
    (old-fashioned term?) "instantaneous codes." Not all compaction codes
    are instantaneous, cf arithmetic or quasi-arithmetic codes.

    We could interpret them as finite nodes in an infinite binary tree, and each of these nodes
    has the property that its path does not pass through any other nodes.

    Also, it seems the sets of nodes are constructed (more or less) by some kind of fractal pattern.
    E.g. set A seems to have a generator pattern (apart from the entry 1):

    A
    / \
    / \
    x x
    / \ / \
    N A N A

    where we paste the root A where it occurs below. The Ns are the terminal nodes, which are the ones
    in your set A, which appears to be listed in order depth then left-to-right. (Left being
    represented as 0, Right as 1).

    I'd guess the sets might be related to compression of infinite stream data??? Perhaps used somehow
    in video codecs? but I don't see exactly how, or know what their names would be.

    Other observations: For all the sets there are infinite paths that have no prefix in the set. Set
    A has uncountably many of these, e.g. 0010101010101... or 0111101011101... (basically, as long as
    odd-numbered digits (other than the first) are 1). All the sets have "enough" nodes so that a
    random path hits a node "almost certainly" (i.e. with probability 1). I don't know if that is
    important.

    Wow, and Kudos again. I think this is all correct.

    But no end of other sets have these same properties - even if the "fractal" property is key. (I
    suppose that might be important when processing an infinite stream, because only a finite amount of
    context data would have to be maintained.

    Yes. Kudos AGAIN to Mike!

    For example, consider (B) where a token terminates if and only if a '11'
    is encountered. There is a code with tokens terminating if and only if
    a '111' is encountered. Or even a code which terminates at '1101010' !

    I worked with these things back in the 20th century, so talking about them is
    a trip down Nostalgia Lane for me. PLEASE help me present puzzles better. Should I have provided more hints to start? Wait longer for responses?


    The codes (A), (B), (C) have names. (B) is the "Fibonacci Code."
    (C) is the "Golomb (or Golomb-Rice) Code with divisor 2."

    I don't know the "official" name of (A) -- in fact I'd be unaware of it
    except that its co-inventor and I both consulted for the same company
    in the mid-1990s. I will call (A) "a version of the Elias Gamma Code with
    a palindromic property." Look again at (A); erase the 2nd, 4th, 6th bits,
    etc. The bit-strings left are all palindromes. (And Mike suggested this.)
    If a data stream is corrupted one can find a synchronization point and then decode BACKWARDS to the point of corruption, perhaps recovering all but one token.


    FINALLY:
    As a hint, I'll provide another puzzle! ... a
    puzzle in the SAME DOMAIN as the original puzzle.
    Guess the relevant domain and both puzzles may fall into place.

    Transformation:
    00 rRR 1
    01 rRR 01
    1 rRR 00

    The coded-token set {1, 01, 00} is a simple prefix code, satisfying the Krafft Equality
    1/2 + 1/4 + 1/4 = 1.

    (BTW, for this and similar codes if the input data ends with an odd number
    of 0's an extra 0 is injected at the end and later removed during decompaction.)
    (The LENGTH of input data is generally knowable.)

    Comment: This compaction code is essentially optimal over a binary alphabet when the probability of '1' is a stationary 29%.

    STILL UNSPOILED:
    Question: What special property does this compaction code have
    which is quite rare among optimal compaction codes?

    Cheers,
    James
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  • From Mike Terry@news.dead.person.stones@darjeeling.plus.com to rec.puzzles on Fri Feb 27 17:29:12 2026
    From Newsgroup: rec.puzzles

    On 27/02/2026 06:25, James Dow Allen wrote:

    (In my most recent post I suggested by example that the "Krafft sum"
    was asymptotically one, where each token in the set contributes 2^(-k)
    to the Krafft sum where k is the number of bits in that token.)


    Mike Terry <news.dead.person.stones@darjeeling.plus.com> posted:

    On 26/02/2026 10:41, James Dow Allen wrote:
    James Dow Allen <user4353@newsgrouper.org.invalid> posted:
    James Dow Allen <user4353@newsgrouper.org.invalid> posted:

    I'm thinking of three sets (of bit-strings) which are conceptually infinite.
    ...
    Each of the infinite sets has the same special and useful property.
    __ What is that property? __


    Not boring at all, but... I don't always see an answer, especially a full answer, and time is
    limited!...

    So looking at your original post, I see some properties, but don't really have a full answer!

    The sequences remind me of Huffman codes, and Huffman codes wouldn't work if sequences of them
    couldn't be uniquely interpreted. Your sets have this property, so we could say they're like an
    infinite set of Huffman codes(?).

    Kudos to Mike Terry! These are exactly like Huffman codes; a more general term is compaction codes. In a finite world, no token will actually be infinite but it is convenient to define mappings of the integers which are unbounded.

    A "Huffman code" is a compaction code which is optimal for some particular probability mass function. But EVERY compaction code with Krafft sum of one will be optimal for SOME distribution.

    Worded differently, all your sets seem to have the property that no two strings start with the same
    prefix.

    Yes. These are called "prefix codes" or "prefix-free codes" or (old-fashioned term?) "instantaneous codes." Not all compaction codes
    are instantaneous, cf arithmetic or quasi-arithmetic codes.

    We could interpret them as finite nodes in an infinite binary tree, and each of these nodes
    has the property that its path does not pass through any other nodes.

    Also, it seems the sets of nodes are constructed (more or less) by some kind of fractal pattern.
    E.g. set A seems to have a generator pattern (apart from the entry 1):

    A
    / \
    / \
    x x
    / \ / \
    N A N A

    where we paste the root A where it occurs below. The Ns are the terminal nodes, which are the ones
    in your set A, which appears to be listed in order depth then left-to-right. (Left being
    represented as 0, Right as 1).

    I'd guess the sets might be related to compression of infinite stream data??? Perhaps used somehow
    in video codecs? but I don't see exactly how, or know what their names would be.

    Other observations: For all the sets there are infinite paths that have no prefix in the set. Set
    A has uncountably many of these, e.g. 0010101010101... or 0111101011101... (basically, as long as
    odd-numbered digits (other than the first) are 1). All the sets have "enough" nodes so that a
    random path hits a node "almost certainly" (i.e. with probability 1). I don't know if that is
    important.

    Wow, and Kudos again. I think this is all correct.

    But no end of other sets have these same properties - even if the "fractal" property is key. (I
    suppose that might be important when processing an infinite stream, because only a finite amount of
    context data would have to be maintained.

    Yes. Kudos AGAIN to Mike!

    Hey, I'm running out of room for storing all my Kudoses! :)


    For example, consider (B) where a token terminates if and only if a '11'
    is encountered. There is a code with tokens terminating if and only if
    a '111' is encountered. Or even a code which terminates at '1101010' !

    I worked with these things back in the 20th century, so talking about them is a trip down Nostalgia Lane for me. PLEASE help me present puzzles better. Should I have provided more hints to start? Wait longer for responses?

    I remember covering Huffman codes back in my student days (studying maths), but more recently I was
    looking at some C code to implement LZ-compression which uses Huffmamn codes, so I was kind of
    primed to recognise this feature. One of my (mild) regrets was that my work (corporate IT stuff)
    didn't really utilise my maths abilities, but hey, I did ok out of it, so no complaints. (I'm
    retired now.)

    I think you are fine with your puzzle presentations so I don't have any recomendations for you.
    This particular puzzle probably suffered a bit from being unclear what its objective was. There was
    no spider which had to catch a fly! :) The topic in itself has some interest (for me) but is maybe
    too technical for lots of people. Also, I think the old days of rec.puzzles are long gone, and
    there are now not many "puzzle people" left... (HenHanna may keep the newsgroup ticking over, but
    very few of his posts are actually "puzzles" in the traditional sense - mostly they're questions
    about language use...)

    Mike.



    The codes (A), (B), (C) have names. (B) is the "Fibonacci Code."
    (C) is the "Golomb (or Golomb-Rice) Code with divisor 2."

    I don't know the "official" name of (A) -- in fact I'd be unaware of it except that its co-inventor and I both consulted for the same company
    in the mid-1990s. I will call (A) "a version of the Elias Gamma Code with
    a palindromic property." Look again at (A); erase the 2nd, 4th, 6th bits, etc. The bit-strings left are all palindromes. (And Mike suggested this.) If a data stream is corrupted one can find a synchronization point and then decode BACKWARDS to the point of corruption, perhaps recovering all but one token.


    FINALLY:
    As a hint, I'll provide another puzzle! ... a
    puzzle in the SAME DOMAIN as the original puzzle.
    Guess the relevant domain and both puzzles may fall into place.

    Transformation:
    00 rRR 1
    01 rRR 01
    1 rRR 00

    The coded-token set {1, 01, 00} is a simple prefix code, satisfying the Krafft Equality
    1/2 + 1/4 + 1/4 = 1.

    (BTW, for this and similar codes if the input data ends with an odd number
    of 0's an extra 0 is injected at the end and later removed during decompaction.)
    (The LENGTH of input data is generally knowable.)

    Comment: This compaction code is essentially optimal over a binary alphabet when the probability of '1' is a stationary 29%.

    STILL UNSPOILED:
    Question: What special property does this compaction code have
    which is quite rare among optimal compaction codes?

    Cheers,
    James

    --- Synchronet 3.21b-Linux NewsLink 1.2
  • From David Entwistle@qnivq.ragjvfgyr@ogvagrearg.pbz to rec.puzzles on Sat Feb 28 02:15:59 2026
    From Newsgroup: rec.puzzles

    On Fri, 27 Feb 2026 06:25:04 GMT, James Dow Allen wrote:

    I worked with these things back in the 20th century, so talking about
    them is a trip down Nostalgia Lane for me. PLEASE help me present
    puzzles better. Should I have provided more hints to start? Wait longer
    for responses?

    Hi James,

    That is interesting. Thanks for the question and explanation. I'm
    following it to some extent.

    Would it be practical to provide a real-World, or 'puzzle-World', scenario where the sequences, with the given properties, provide a solution to a problem the inhabitants faced? Crash survivors, on two islands,
    communicating with limited means - that sort of thing... I find that understanding a problem gives weight to the solution.

    I like pictures and there is a nice one (possibly related) here:

    https://en.wikipedia.org/wiki/Zeckendorf%27s_theorem

    Best wishes,
    --
    David Entwistle
    --- Synchronet 3.21d-Linux NewsLink 1.2
  • From James Dow Allen@user4353@newsgrouper.org.invalid to rec.puzzles on Sat Feb 28 06:07:10 2026
    From Newsgroup: rec.puzzles


    David Entwistle <qnivq.ragjvfgyr@ogvagrearg.pbz> posted:

    Would it be practical to provide a real-World, or 'puzzle-World', scenario where the sequences, with the given properties, provide a solution to a problem the inhabitants faced? Crash survivors, on two islands, communicating with limited means - that sort of thing... I find that understanding a problem gives weight to the solution.

    Maybe, but I probably lack the imagination to come up with such an idea. Communication with aliens? A property of optimal compaction is that the compressed form appears random, so indecipherable.

    There are some documents from the early 1600s which allegedly contain
    cryptic messages. A task for those with good intuition is to guess
    whether such messages are genuine, or arise by chance. Would 1 or 2
    of such alleged encryptions be of interest? But the aliens could begin
    by listing the coded integers, much as I did in (B) of the first post
    in this thread.

    I like pictures and there is a nice one (possibly related) here:

    https://en.wikipedia.org/wiki/Zeckendorf%27s_theorem

    Yes, that article and its references show why (B) above ("the Fibonacci code") works. I notice cites to a paper which makes the observation I made, that strings other than '11' can be used as the delimiting comma, also achieving instantaneous decoding with the Krafft equality implying optimality.

    I recognized the name of the author -- Jarek Duda. You can see at
    https://arxiv.org/pdf/1206.4555
    that I helped him with a combinatorial problem many years ago.
    Specifically I showed him how to replace a bound of (QQQ + 2.71828)
    with (QQQ + 0.57721)*, a rather amazing change since Euler's number
    gets changed to the seemingly-unrelated Euler's constant.
    * - The actual improvement was similar to, but less than, this
    (2.71828 - 0.57721) but I cannot remember details.

    Cheers,
    James
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  • From James Dow Allen@user4353@newsgrouper.org.invalid to rec.puzzles on Sat Feb 28 06:13:22 2026
    From Newsgroup: rec.puzzles


    Just a reminder that one puzzle has not yet been explicitly solved.
    The "puzzle" isn't difficult, but stating the solution should elicit
    at least a tiny "WOW!"

    STILL UNSPOILED:
    Question: What special property does the compaction code [shown below] have
    which is quite rare among optimal compaction codes?

    James Dow Allen <user4353@newsgrouper.org.invalid> posted:
    Mike Terry <news.dead.person.stones@darjeeling.plus.com> posted:
    On 26/02/2026 10:41, James Dow Allen wrote:
    James Dow Allen <user4353@newsgrouper.org.invalid> posted:
    James Dow Allen <user4353@newsgrouper.org.invalid> posted:

    FINALLY:
    As a hint, I'll provide another puzzle! ... a
    puzzle in the SAME DOMAIN as the original puzzle.
    Guess the relevant domain and both puzzles may fall into place.

    Transformation:
    00 rRR 1
    01 rRR 01
    1 rRR 00

    Comment: This compaction code is essentially optimal over a binary alphabet when the probability of '1' is a stationary 29%.

    STILL UNSPOILED:
    Question: What special property does this compaction code have
    which is quite rare among optimal compaction codes?

    Cheers,
    James
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  • From David Entwistle@qnivq.ragjvfgyr@ogvagrearg.pbz to rec.puzzles on Sun Mar 1 10:55:33 2026
    From Newsgroup: rec.puzzles

    On Sat, 28 Feb 2026 06:13:22 GMT, James Dow Allen wrote:

    Just a reminder that one puzzle has not yet been explicitly solved. The "puzzle" isn't difficult, but stating the solution should elicit at
    least a tiny "WOW!"

    I think I'm slightly lost, but did find the following web page somewhat illuminating:

    https://james.fabpedigree.com/appixm.htm

    In general, in this puzzle, we could be talking about reducing the size of source code for very constrained computer architectures; is that correct?

    I did like the last paragraph comment, from the web page, "decoded in
    either direction". That is neat. You may have already mention that here.

    Best wishes,
    --
    David Entwistle
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  • From David Entwistle@qnivq.ragjvfgyr@ogvagrearg.pbz to rec.puzzles on Mon Mar 2 02:45:39 2026
    From Newsgroup: rec.puzzles

    On Sun, 1 Mar 2026 10:55:33 -0000 (UTC), David Entwistle wrote:

    In general, in this puzzle, we could be talking about reducing the size
    of source code for very constrained computer architectures; is that
    correct?

    Apologies, I think I meant to say reducing the size of machine code, not source code. So, variable-length binary information. It's been a long time since I looked at anything like that. I suspect my experience-bias to a
    bus architecture is is proving a barrier to seeing the environment.
    --
    David Entwistle
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