This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A343930 #32 Jul 02 2021 11:32:43
%S A343930 1,2,30,33,37,83,149,262,4030,31969,140225,182730,724754,2337094,
%T A343930 3985753,4195221,4541725
%N A343930 Numbers k such that Sum_{j=1..k} (-j)^j == 1 (mod k).
%t A343930 q[n_] := n == 1 || Mod[Sum[PowerMod[-k, k, n], {k, 1, n}], n] == 1; Select[Range[5000], q] (* _Amiram Eldar_, May 04 2021 *)
%o A343930 (PARI) isok(n) = sum(k=1, n, Mod(-k, n)^k)==1;
%Y A343930 Cf. A188776, A341437, A343931, A343933.
%K A343930 nonn,more
%O A343930 1,2
%A A343930 _Seiichi Manyama_, May 04 2021
%E A343930 a(11)-a(13) from _Chai Wah Wu_, May 04 2021
%E A343930 a(14) from _Martin Ehrenstein_, May 05 2021
%E A343930 a(15)-a(17) from _Martin Ehrenstein_, May 08 2021