A380656 a(n) is the number of divisors d such that -d^n mod n = d.

0, 1, 0, 0, 0, 2, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 3, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 0, 1, 0, 0, 0, 4, 0, 0, 0, 4, 0, 1, 0, 1, 0, 1, 0, 2, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 2, 1, 1, 0, 1, 0, 1, 0, 1, 0, 0

Offset: 1

Author

Juri-Stepan Gerasimov, Feb 03 2025

Keywords

• nonn

Crossrefs

Cf. A000005, A371883.

Programs

Magma

[#[d: d in Divisors(n) | -d^n mod n eq d]: n in [1..100]];

Mathematica

a[n_] := DivisorSum[n, 1 &, Mod[-PowerMod[#, n, n], n] == # &]; Array[a, 100] (* Amiram Eldar, Feb 04 2025 *)