A055703 Numbers k such that k | sigma_9(k) - phi(k)^9.

1, 2, 12, 54, 76, 90, 216, 423, 514, 531, 621, 2166, 2241, 2772, 2976, 4752, 5154, 5400, 5481, 6264, 7290, 7344, 9018, 9144, 9470, 9555, 14094, 14904, 19494, 21222, 23780, 25848, 28323, 34830, 34911, 38220, 40122, 48768, 49079, 55782, 59400

Offset: 1

Author

Robert G. Wilson v, Jun 09 2000

Keywords

• nonn

Comments

sigma_9(k) is the sum of the 9th powers of the divisors of k (A013957).

Links

• Amiram Eldar, Table of n, a(n) for n = 1..250

Crossrefs

Cf. A000010, A013957.

Programs

Mathematica

Do[If[Mod[DivisorSigma[9, n]-EulerPhi[n]^9, n]==0, Print[n]], {n, 1, 10^5}]

PARI

isok(n) = !((sigma(n, 9) - eulerphi(n)^9) % n); \\ Michel Marcus, Mar 02 2014

Extensions

Definition corrected by Michel Marcus, Mar 02 2014