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A115510 a(1)=1. a(n) is smallest positive integer not occurring earlier in the sequence such that a(n) and a(n-1) have at least one 1-bit in the same position when they are written in binary. 6
1, 3, 2, 6, 4, 5, 7, 9, 8, 10, 11, 12, 13, 14, 15, 17, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 33, 32, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65, 64, 66, 67, 68, 69, 70, 71, 72 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Sequence is a permutation of the positive integers. A115511 is the inverse permutation.

(4,6,5) is a 3-cycle and (2^k,2^k+1) for k = 1 and k > 2 are 2-cycles; all other numbers are fixed points. - Klaus Brockhaus, Jan 24 2006

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..1025

EXAMPLE

a(3) = 2 = 10 in binary. Among the positive integers not occurring among the first 3 terms of the sequence (4 = 100 in binary, 5 = 101 in binary, 6 = 110 in binary,...), 6 is the smallest that shares at least one 1-bit with a(3) when written in binary. So a(4) = 6.

MATHEMATICA

Block[{a = {1}, k}, Do[k = 1; While[Or[BitAnd[Last@ a, k ] == 0, MemberQ[a, k]], k++]; AppendTo[a, k], {71}]; a] (* Michael De Vlieger, Sep 07 2017 *)

CROSSREFS

Cf. A109812, A115511, A226077.

Sequence in context: A286367 A196047 A106409 * A230598 A245446 A070264

Adjacent sequences:  A115507 A115508 A115509 * A115511 A115512 A115513

KEYWORD

easy,nonn

AUTHOR

Leroy Quet, Jan 23 2006

EXTENSIONS

More terms from Klaus Brockhaus, Jan 24 2006

STATUS

approved

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Last modified July 26 17:37 EDT 2021. Contains 346294 sequences. (Running on oeis4.)