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 A379864 #13 Jan 05 2025 09:58:38
%S A379864 1,4,54,1334,48816,2383682,146036788,10781227690,932243805168,
%T A379864 92452039842626,10346916215343564,1290195352404492602,
%U A379864 177396099439904780200,26665611450484642809058,4350590232650155748720484,765717105431099707449714218
%N A379864 Expansion of e.g.f. (1/x) * Series_Reversion( x * (exp(-x) - x)^2 ).
%H A379864 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A379864 E.g.f. A(x) satisfies A(x) = 1/(exp(-x*A(x)) - x*A(x))^2.
%F A379864 E.g.f.: B(x)^2, where B(x) is the e.g.f. of A379867.
%F A379864 a(n) = 2 * n! * Sum_{k=0..n} (3*n-k+2)^(k-1) * binomial(3*n-k+2,n-k)/k!.
%o A379864 (PARI) a(n) = 2*n!*sum(k=0, n, (3*n-k+2)^(k-1)*binomial(3*n-k+2, n-k)/k!);
%Y A379864 Cf. A379867.
%K A379864 nonn
%O A379864 0,2
%A A379864 _Seiichi Manyama_, Jan 04 2025