A380833 a(n) is the number of divisors d of n satisfying (-d)^n mod n = d.
0, 1, 0, 1, 0, 2, 0, 1, 0, 2, 0, 2, 0, 2, 1, 1, 0, 2, 0, 2, 0, 2, 0, 1, 0, 2, 0, 2, 0, 4, 0, 1, 0, 2, 1, 2, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 1, 0, 2, 0, 1, 0, 4, 0, 2, 0, 2, 0, 2, 0, 2, 0, 1, 0, 3, 0, 2, 0, 2, 0, 3, 0, 2, 0, 1, 0, 3, 1, 1, 0, 2, 0, 1, 0, 2, 0, 2
Offset: 1
Keywords
Programs
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Magma
[#[d: d in Divisors(n) | (-d)^n mod n eq d]: n in [1..100]];
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Mathematica
a[n_] := DivisorSum[n, 1 &, PowerMod[-#, n, n] == # &]; Array[a, 100] (* Amiram Eldar, Feb 06 2025 *)