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 A380666 #8 Jan 30 2025 03:52:37
%S A380666 1,3,33,670,20193,812736,41056921,2499780144,178288822305,
%T A380666 14584953692800,1346528845766481,138513476506770432,
%U A380666 15711724851356153857,1948422564510092267520,262263690685637016402825,38082186820362623941236736,5933845220766237850177220289,987599486681637240983472930816
%N A380666 Expansion of e.g.f. (1/x) * Series_Reversion( x * (1 - x)^2 * exp(-x/(1 - x)^2) ).
%H A380666 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A380666 E.g.f. A(x) satisfies A(x) = exp(x * A(x)/(1 - x*A(x))^2)/(1 - x*A(x))^2.
%F A380666 a(n) = n! * Sum_{k=0..n} (n+1)^(k-1) * binomial(3*n+k+1,n-k)/k!.
%o A380666 (PARI) a(n) = n!*sum(k=0, n, (n+1)^(k-1)*binomial(3*n+k+1, n-k)/k!);
%Y A380666 Cf. A380665.
%K A380666 nonn
%O A380666 0,2
%A A380666 _Seiichi Manyama_, Jan 30 2025