A390213 Number of divisors d of n such that d^(n/d) == d (mod (n/d)).

1, 2, 2, 3, 2, 4, 2, 3, 3, 4, 2, 4, 2, 4, 4, 4, 2, 5, 2, 5, 4, 4, 2, 5, 3, 4, 3, 4, 2, 5, 2, 4, 4, 4, 4, 6, 2, 4, 4, 4, 2, 6, 2, 4, 4, 4, 2, 6, 3, 5, 4, 5, 2, 5, 4, 4, 4, 4, 2, 8, 2, 4, 4, 5, 4, 5, 2, 5, 4, 5, 2, 7, 2, 4, 5, 4, 4, 6, 2, 5, 4, 4, 2, 6, 4, 4, 4, 4

Offset

1,2

Links

Table of n, a(n) for n=1..88.

Mathematica

a[n_] := DivisorSum[n, 1 &, PowerMod[#, n/#, n/#] == Mod[#, n/#] &]; Array[a, 100] (* Amiram Eldar, Nov 06 2025 *)

Crossrefs

Cf. A000005, A384237, A389781.

Sequence in context: A205562 A217984 A196437 * A106491 A386776 A073184

Adjacent sequences: A390210 A390211 A390212 * A390214 A390215 A390216

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, Oct 29 2025

Status

approved