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 A375830 #8 Aug 31 2024 08:32:46
%S A375830 1,0,0,6,0,60,1080,1680,80640,1058400,8316000,257463360,3692304000,
%T A375830 66421555200,1801442522880,34333457558400,905811504998400,
%U A375830 25171307671910400,646170363904665600,20523302430017587200,637272191855819520000,20620406757762459648000
%N A375830 E.g.f. satisfies A(x) = 1/(1 - x^2*A(x))^x.
%F A375830 a(n) = n! * Sum_{k=0..floor(n/2)} (k+1)^(n-2*k-1) * |Stirling1(k,n-2*k)|/k!.
%o A375830 (PARI) a(n) = n!*sum(k=0, n\2, (k+1)^(n-2*k-1)*abs(stirling(k, n-2*k, 1))/k!);
%Y A375830 Cf. A375831.
%K A375830 nonn
%O A375830 0,4
%A A375830 _Seiichi Manyama_, Aug 30 2024