A232067 Numbers k such that sigma(k^2) and Sum_{d|k} d*sigma(d) are both multiples of k.

1, 39, 793, 2379, 7137, 76921, 230763, 692289, 2076867, 8329831, 24989493, 53695813, 74968479, 161087439, 224905437, 243762649, 324863409, 375870691, 483262317, 731287947, 1127612073, 1449786951, 2094136707, 2193863841, 2631094837, 3382836219, 3606816823

Offset: 1

Author

M. F. Hasler, Nov 24 2013

Keywords

• nonn

Comments

Intersection of A069520 and A232354.

Can these numbers be characterized as the terms of A232354 which do not have a factor in {11, 1093, ...}? Is this A090814, or (a subsequence of) A126197?

Links

• Donovan Johnson, Table of n, a(n) for n = 1..70

Crossrefs

Cf. A000203, A069520, A232354.

Programs

Mathematica

fQ[n_] := Mod[DivisorSigma[1, n^2], n] == 0 && Mod[DivisorSum[n, #*DivisorSigma[1, #] &], n] == 0; Select[Range[100000], fQ] (* T. D. Noe, Nov 25 2013 *)