A094469 Numbers k such that sum of 11th powers of divisors of k is divisible by the square of Euler-phi of k.

1, 2, 3, 6, 1645, 3290, 4935, 9870, 3831674, 11495022, 346014339, 692028678

Offset: 1

Author

Labos Elemer, May 19 2004

Keywords

• nonn
• more

Crossrefs

Cf. A000010, A013959, A015763, A091285.

Programs

Mathematica

Do[ If[ Mod[ DivisorSigma[11, n], EulerPhi[n]^2] == 0, Print[n]], {n, 10^7}] (* Robert G. Wilson v, May 23 2004 *)

PARI

isok(k) = (sigma(k, 11) % eulerphi(k)^2) == 0; \\ Michel Marcus, Mar 07 2020

Formula

A013959(k)/A000010(k)^2 is an integer.

Extensions

a(9) from Robert G. Wilson v, May 23 2004

a(10) from Labos Elemer, May 26 2004

a(6) corrected and a(11)-a(12) added by Amiram Eldar, Mar 07 2020