A093038 Numbers k such that sum of 5th powers of divisors of k is divisible by the square of Euler-phi of k.

1, 2, 3, 6, 322, 966, 473732, 1420296, 6655780894

Offset: 1

Author

Labos Elemer, May 19 2004

Keywords

• nonn
• more

Comments

No more terms through 10^9. - Ryan Propper, Jan 09 2007

Crossrefs

Cf. A000010, A015763, A091285.

Programs

Mathematica

Do[ If[ Mod[ DivisorSigma[5, n], EulerPhi[n]^2] == 0, Print[n]], {n, 10^7}] (* Robert G. Wilson v, May 23 2004 *)

PARI

isok(k) = (sigma(k, 5) % eulerphi(k)^2) == 0; \\ Michel Marcus, Mar 07 2020

Formula

A001160(k)/A000010(k)^2 is an integer.

Extensions

a(9) from Amiram Eldar, Mar 07 2020