A063514 a(n) = sigma(n) mod phi(n).

0, 0, 0, 1, 2, 0, 2, 3, 1, 2, 2, 0, 2, 0, 0, 7, 2, 3, 2, 2, 8, 6, 2, 4, 11, 6, 4, 8, 2, 0, 2, 15, 8, 6, 0, 7, 2, 6, 8, 10, 2, 0, 2, 4, 6, 6, 2, 12, 15, 13, 8, 2, 2, 12, 32, 0, 8, 6, 2, 8, 2, 6, 32, 31, 36, 4, 2, 30, 8, 0, 2, 3, 2, 6, 4, 32, 36, 0, 2, 26, 13, 6, 2

Offset: 1

Author

Labos Elemer, Jul 31 2001

Keywords

• nonn
• easy

Comments

If a(n) = 0, then n is a balanced number (A020492).

Links

• Harry J. Smith, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A000010, A000203, A020492, A023897.

Programs

Magma

[SumOfDivisors(n) mod EulerPhi(n): n in [1..85]]; // Bruno Berselli, Jan 31 2013

Mathematica

a[n_] := Mod[DivisorSigma[1, n], EulerPhi[n]]; Array[a, 100] (* Amiram Eldar, Dec 25 2024 *)

PARI

a(n) = { sigma(n)%eulerphi(n) } \\ Harry J. Smith, Aug 24 2009

Formula

a(p^2) = 2*p+1, for prime p >= 5. - Michel Marcus, Apr 07 2020