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 A386310 #49 Aug 30 2025 02:52:42
%S A386310 1,2,1,2,1,2,1,3,2,2,1,2,1,2,1,3,1,4,1,2,1,2,1,3,2,2,3,2,1,2,1,4,1,2,
%T A386310 1,4,1,2,1,3,1,2,1,2,2,2,1,4,2,4,1,2,1,6,1,3,1,2,1,2,1,2,2,5,1,2,1,2,
%U A386310 1,2,1,6,1,2,2,2,1,2,1,4,3,2,1,2,1,2,1,3,1,4,1,2,1,2,1,5,1,4,2,4
%N A386310 Number of divisors d of n such that 2*d^d == 0 (mod n).
%t A386310 Table[Length[Select[Divisors[n], PowerMod[#, #, n] == Mod[n - PowerMod[#, #, n], n] &]], {n, 1, 100}] (* _Vaclav Kotesovec_, Aug 23 2025 *)
%o A386310 (Magma) [1 + #[d: d in [1..n-1] | n mod d eq 0 and Modexp(d,d,n) eq -Modexp(d,d,n) mod n]: n in [1..100]];
%o A386310 (PARI) a(n) = sumdiv(n, d, 2*Mod(d, n)^d == 0); \\ _Michel Marcus_, Aug 30 2025
%Y A386310 Cf. A000005, A385429, A385662, A386930.
%K A386310 nonn,new
%O A386310 1,2
%A A386310 _Juri-Stepan Gerasimov_, Aug 20 2025