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

1,2

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

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 *)

Crossrefs

Cf. A000203, A069520, A232354.

Sequence in context: A194133 A069520 A232354 * A247222 A268983 A293918

Adjacent sequences: A232064 A232065 A232066 * A232068 A232069 A232070

Keyword

nonn

Author

M. F. Hasler, Nov 24 2013

Status

approved