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 A363737 #15 Jul 03 2023 01:00:25
%S A363737 1,0,2,-6,2,0,2,-1680,10082,0,2,-665280,2,0,3632428802,-36843206400,2,
%T A363737 0,2,-670442572800,3379030566912002,0,2,-71812452903064473600,
%U A363737 1077167364120207360002,0,10002268381116211200002,-3497296636753920000,2,0,2
%N A363737 a(n) = n! * Sum_{d|n} (-1)^(d+1) / (d! * (n/d)!).
%F A363737 E.g.f.: Sum_{k>0} (1 - exp(-x^k))/k!.
%F A363737 If p is an odd prime, a(p) = 2.
%t A363737 a[n_] := n! * DivisorSum[n, (-1)^(#+1)/(#! * (n/#)!) &]; Array[a, 30] (* _Amiram Eldar_, Jul 03 2023 *)
%o A363737 (PARI) a(n) = n!*sumdiv(n, d, (-1)^(d+1)/(d!*(n/d)!));
%Y A363737 Cf. A121860, A132962, A363736.
%K A363737 sign
%O A363737 1,3
%A A363737 _Seiichi Manyama_, Jun 18 2023