A232703 Numbers k that divide sigma(k) + sigma(k^2).

1, 2, 185, 113125, 535350201, 71373089217, 82225037115, 156231750533, 268821356379

Offset: 1

Author

Alex Ratushnyak, Nov 28 2013

Keywords

• nonn
• hard
• more

Comments

a(10) > 10^12. - Giovanni Resta, Jun 10 2016

Crossrefs

Cf. A000203 (sigma(n) = sum of divisors of n).

Cf. A232547, A065764, A247222.

Programs

Mathematica

Select[Range[150000], Mod[Plus @@ DivisorSigma[1, {#, #^2}], #] == 0 &] (* Giovanni Resta, Jun 10 2016 *)

Extensions

a(6)-a(9) from Giovanni Resta, Jun 10 2016