A081354 Numbers k such that sigma(k^2) modulo 4 = 3.

2, 4, 5, 6, 8, 12, 13, 14, 15, 16, 17, 18, 22, 24, 28, 29, 32, 35, 36, 37, 38, 39, 41, 42, 44, 45, 46, 48, 50, 51, 53, 54, 55, 56, 61, 62, 64, 66, 72, 73, 76, 84, 86, 87, 88, 89, 91, 92, 94, 95, 96, 97, 98, 100, 101, 105, 108, 109, 111, 112, 113, 114, 115, 117, 118, 119, 123

Offset: 1

Author

Benoit Cloitre, Apr 20 2003

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A065764.

Programs

Mathematica

Select[Range[150],Mod[DivisorSigma[1,#^2],4]==3&] (* Harvey P. Dale, Dec 18 2012 *)

Formula

Probably a(n)/n -> 2.