A343930 Numbers k such that Sum_{j=1..k} (-j)^j == 1 (mod k).
1, 2, 30, 33, 37, 83, 149, 262, 4030, 31969, 140225, 182730, 724754, 2337094, 3985753, 4195221, 4541725
Offset: 1
Programs
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Mathematica
q[n_] := n == 1 || Mod[Sum[PowerMod[-k, k, n], {k, 1, n}], n] == 1; Select[Range[5000], q] (* Amiram Eldar, May 04 2021 *) -
PARI
isok(n) = sum(k=1, n, Mod(-k, n)^k)==1;
Extensions
a(11)-a(13) from Chai Wah Wu, May 04 2021
a(14) from Martin Ehrenstein, May 05 2021
a(15)-a(17) from Martin Ehrenstein, May 08 2021