A097503 Numbers k such that A000203(k) = sigma(k) is not divisible by 6.

1, 2, 3, 4, 7, 8, 9, 12, 13, 16, 18, 19, 21, 25, 27, 28, 31, 32, 36, 37, 39, 43, 48, 49, 50, 52, 57, 61, 63, 64, 67, 72, 73, 75, 76, 79, 81, 84, 91, 93, 97, 98, 100, 103, 108, 109, 111, 112, 117, 121, 124, 127, 128, 129, 133, 139, 144, 148, 151, 156, 157, 162, 163, 169

Offset: 1

Author

Labos Elemer, Aug 23 2004

Keywords

• nonn

Comments

Positions of nonzero terms in A084301. - Ivan Neretin, Jan 26 2017

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A084301.

Complement of A074627.

Programs

Mathematica

Select[Range[170], ! Divisible[DivisorSigma[1, #], 6] &] (* Ivan Neretin, Jan 26 2017 *)

PARI

isok(n) = (sigma(n) % 6) != 0; \\ Michel Marcus, Jan 26 2017

Extensions

Definition corrected by Ivan Neretin, Jan 26 2017