A161396 a(n) = the smallest positive integer that contains the same number of 1's as n when a(n) and n are written in binary, is not coprime to n, and is not a divisor of n.
4, 6, 8, 10, 9, 14, 16, 6, 6, 22, 9, 26, 21, 27, 32, 34, 10, 38, 6, 14, 14, 46, 9, 35, 14, 15, 21, 58, 27, 62, 64, 6, 6, 14, 10, 74, 14, 15, 6, 82, 22, 86, 14, 27, 30, 94, 9, 14, 14, 15, 14, 106, 15, 110, 21, 15, 30, 118, 27, 122, 93, 111, 128, 10, 9, 134, 6
Offset: 2
Examples
6_10 (6 in decimal) is 110_2 (110 in binary). 9_10 = 1001_2, which contains the same number of ones in the binary expansion. 9 isn't coprime to 6; they share prime factor 3 and 9 isn't a divisor of 6. No positive integer less than 9 has these properties. Therefore, a(6) = 9.
Links
- Rémy Sigrist, Table of n, a(n) for n = 2..10000
Extensions
Offset corrected and more terms from Rémy Sigrist, Apr 15 2017