A145254 a(n) = the smallest positive integer that is non-coprime to n and has the same number of 1's in its binary representation as n.

2, 3, 2, 5, 3, 7, 2, 3, 5, 11, 3, 13, 7, 15, 2, 17, 3, 19, 5, 7, 11, 23, 3, 25, 13, 15, 7, 29, 15, 31, 2, 3, 6, 7, 3, 37, 14, 15, 5, 41, 7, 43, 11, 15, 23, 47, 3, 7, 14, 15, 13, 53, 15, 55, 7, 15, 29, 59, 15, 61, 31, 63, 2, 5, 3, 67, 6, 21, 7, 71, 3, 73, 14, 15, 14, 77, 15, 79, 5, 21, 14, 83

Offset: 2

Author

Leroy Quet, Oct 05 2008

Keywords

• base
• nonn
• look

Links

• Michael De Vlieger, Table of n, a(n) for n = 2..16384

Crossrefs

Cf. A145255, A145256, A145257.

Programs

Mathematica

Table[Function[k, SelectFirst[Range[2, n], And[! CoprimeQ[#, n], DigitCount[#, 2, 1] == k] &]]@ DigitCount[n, 2, 1], {n, 2, 83}] (* Michael De Vlieger, Oct 26 2017 *)

PARI

a(n) = {my(k = 1, hn = hammingweight(n)); while ((hammingweight(k) != hn) || (gcd(n, k) == 1), k++); k;} \\ Michel Marcus, Oct 27 2017

Extensions

Extended by Ray Chandler, Nov 03 2008