A143113 a(n) = the smallest positive integer that is coprime to n and has the same number of 1's in its binary representation as n has in binary.

1, 1, 5, 1, 3, 5, 11, 1, 5, 3, 7, 5, 7, 11, 23, 1, 3, 5, 7, 3, 11, 7, 15, 5, 7, 7, 23, 11, 15, 23, 47, 1, 5, 3, 11, 5, 7, 7, 23, 3, 7, 11, 15, 7, 23, 15, 31, 5, 11, 7, 23, 7, 15, 23, 31, 11, 23, 15, 31, 23, 31, 47, 95, 1, 3, 5, 7, 3, 7, 11, 15, 5, 7, 7, 23, 7, 15, 23, 31, 3, 7, 7, 15, 11

Offset

1,3

Links

Owen Whitby, Table of n, a(n) for n = 1..200

Example

For n = 27: 27 in binary is 11011, which has four 1's. The positive integers that each have four 1's in their binary representations are 15,23,27,29, etc. The smallest of these that is coprime to 27 is 23. So a(27) = 23.

Mathematica

cp[n_]:=Module[{k=1, dcn=DigitCount[n, 2, 1]}, While[!CoprimeQ[n, k] || DigitCount[ k, 2, 1] != dcn, k++]; k]; Array[cp, 90] (* Harvey P. Dale, Aug 13 2012 *)

Crossrefs

Cf. A143114.

Sequence in context: A213815 A300428 A300475 * A053544 A174879 A327965

Adjacent sequences: A143110 A143111 A143112 * A143114 A143115 A143116

Keyword

base,nonn

Author

Leroy Quet, Jul 25 2008

Extensions

a(31) to a(200) from Owen Whitby, Oct 22 2008

Status

approved