The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A147991 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A147991

Sequence S such that 1 is in S and if x is in S, then 3x-1 and 3x+1 are in S.
(history; published version)

#73 by Alois P. Heinz at Mon Jan 30 18:46:54 EST 2023

STATUS

editing

approved

#72 by Alois P. Heinz at Mon Jan 30 18:46:49 EST 2023

CROSSREFS

Column k=3 of A360099.

STATUS

approved

editing

#71 by Alois P. Heinz at Sun Jan 29 10:29:55 EST 2023

STATUS

editing

approved

#70 by Alois P. Heinz at Sun Jan 29 10:29:42 EST 2023

FORMULA

a(n) mod 2 = A030300(n). - Alois P. Heinz, Jan 29 2023

CROSSREFS

Cf. A030300.

STATUS

approved

editing

#69 by Michel Marcus at Sun Feb 06 03:45:00 EST 2022

STATUS

reviewed

approved

#68 by Joerg Arndt at Sun Feb 06 02:34:22 EST 2022

STATUS

proposed

reviewed

#67 by Michel Marcus at Sun Feb 06 02:13:33 EST 2022

STATUS

editing

proposed

Discussion

Sun Feb 06

02:16

Kevin Ryde: Yes.

#66 by Michel Marcus at Sun Feb 06 02:13:19 EST 2022

LINKS

J. H. Loxton and A. J. van der Poorten, <a href="https://doi.org/10.4064/aa-49-2-193-203">An Awful Problem About Integers in Base Four</a>, Acta Arithmetica, volume 49, 1987, pages 193-203. In section 7, John Selfridge and Carole Lacampagne ask whether every k != 0 (mod 3) is the quotient of two terms of this sequence (cf. A351243 and A006288).

Discussion

Sun Feb 06

02:13

Michel Marcus: or like this ?

#65 by Kevin Ryde at Sun Feb 06 02:11:57 EST 2022

PROG

(PARI) a(n) = fromdigits(apply(b->if(b, 1, -1), binary(n)), 3); \\ Kevin Ryde, Feb 06 2022

STATUS

proposed

editing

#64 by Kevin Ryde at Sun Feb 06 02:09:41 EST 2022

STATUS

editing

proposed