The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A136808

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A136808

Numbers k such that k and k^2 use only the digits 0, 1 and 2.
(history; published version)

#55 by Kevin Ryde at Fri Nov 15 20:34:24 EST 2024

STATUS

editing

proposed

#54 by Kevin Ryde at Fri Nov 15 20:34:01 EST 2024

CROSSREFS

Cf. A278038, A007088.

STATUS

proposed

editing

#53 by Alois P. Heinz at Fri Nov 15 19:52:08 EST 2024

STATUS

editing

proposed

Discussion

Fri Nov 15

20:18

Kevin Ryde: What was Harvey P. Dale's advice when you asked about that code?  The history suggests crossref note was MFH later, and who programmed to the same k = digits 0,1 only.  Presumably one or both had/has good reason as to why ...

#52 by Alois P. Heinz at Fri Nov 15 19:51:26 EST 2024

COMMENTS

Not a subsequence of A278038 (binary numbers without '111'). A counter example counterexample is 10^2884 + 10^2880 + 10^2872 + 10^2857 + 10^2497 + 10^2426 + 10^2285 + 10^2004 + 10^1443 + 10^1442 + 10^1441 + 10^881 + 10^600 + 10^459 + 10^388 + 10^27 + 10^12 + 10^4 + 1. Is this sequence a subsequence of the binary numbers A007088? - Jovan Radenkovicc, Nov 15 2024

#51 by Alois P. Heinz at Fri Nov 15 19:51:11 EST 2024

STATUS

proposed

editing

#50 by Alois P. Heinz at Fri Nov 15 14:55:12 EST 2024

STATUS

editing

proposed

Discussion

Fri Nov 15

19:51

Alois P. Heinz: https://en.wikipedia.org/wiki/Counterexample

#49 by Alois P. Heinz at Fri Nov 15 14:54:49 EST 2024

MATHEMATICA

Select[FromDigits/@Tuples[{0, 1}, 7], Union[Take[DigitCount[#^2], {3, 9}]]=={0}&] (* Harvey P. Dale, May 29 2013 *) - (* possibly incorrect!!! - _Jovan Radenkovicc_, Nov 15 2024 *)

STATUS

proposed

editing

#48 by Andrew Howroyd at Fri Nov 15 13:34:04 EST 2024

STATUS

editing

proposed

Discussion

Fri Nov 15

14:22

Michel Marcus: Yes good idea

#47 by Andrew Howroyd at Fri Nov 15 13:33:21 EST 2024

COMMENTS

Not a subsequence of A278038 (binary numbers without '111'). A counter example is 10^2884 + 10^2880 + 10^2872 + 10^2857 + 10^2497 + 10^2426 + 10^2285 + 10^2004 + 10^1443 + 10^1442 + 10^1441 + 10^881 + 10^600 + 10^459 + 10^388 + 10^27 + 10^12 + 10^4 + 1. Is this sequence a subsequence of the binary numbers A007088? - Jovan Radenkovicc, Nov 15 2024

STATUS

proposed

editing

Discussion

Fri Nov 15

13:34

Andrew Howroyd: Perhaps we can include the counter example like this?

#46 by Michel Marcus at Fri Nov 15 09:30:21 EST 2024

STATUS

editing

proposed

Discussion

Fri Nov 15

09:47

Jovan Radenkovicc: No, I don't, because I constructed this number in more than 15 tries of Magma calculator.

12:53

Andrew Howroyd: I don't understand why you ask if this sequence is a subsequence of the binary numbers? Your example contains several 2's.

12:59

Andrew Howroyd: Ok I didn't see the = sign in the middle.