A072462 Numbers k such that sigma(k) == 3 (mod 4).

2, 4, 8, 16, 18, 25, 32, 36, 64, 72, 98, 128, 144, 162, 169, 196, 225, 242, 256, 288, 289, 324, 392, 484, 512, 576, 648, 722, 784, 841, 882, 968, 1024, 1058, 1152, 1225, 1250, 1296, 1369, 1444, 1458, 1521, 1568, 1681, 1764, 1922, 1936, 2025, 2048, 2116, 2178

Offset: 1

Author

Labos Elemer, Jun 19 2002

Keywords

• nonn

Links

• Ray Chandler, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A028982, A072461.

Programs

Mathematica

Select[Range[2200], Mod[DivisorSigma[1, #], 4] == 3 &] (* Michael De Vlieger, Aug 10 2023 *)

PARI

isok(n) = ((sigma(n) % 4) == 3); \\ Michel Marcus, Dec 19 2013

Extensions

Name edited by Michel Marcus, Dec 19 2013