A195864 Numbers k such that sigma(k) + tau(k) is a perfect number (A000396).

3, 14, 15, 168, 326, 5414, 33357341, 4324809536

Offset: 1

Author

Jeff Kruse, Oct 26 2011

Keywords

• nonn
• more

Comments

A002093(848) < a(9) <= 1155321467378283328. - Donovan Johnson, Nov 03 2011

Crossrefs

Cf. A000396, A002093, A007503 (sigma(n) + tau(n)).

Programs

Mathematica

perfect = {6, 28, 496, 8128, 33550336, 8589869056, 137438691328}; Select[Range[10000], MemberQ[perfect, DivisorSigma[0, #] + DivisorSigma[1, #]] &] (* T. D. Noe, Nov 03 2011 *)

Extensions

a(8) from Donovan Johnson, Nov 03 2011