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 A369402 #14 Feb 16 2024 09:53:49
%S A369402 1,2,5,17,72,330,1554,7490,36992,186582,956573,4967425,26070960,
%T A369402 138081690,737120376,3962039625,21424392088,116467354320,636141911420,
%U A369402 3489357591052,19213097243736,106158276425242,588409936029990,3270832234633026,18229957695363048
%N A369402 Expansion of (1/x) * Series_Reversion( x / (1+x)^2 * (1-x^3)^3 ).
%H A369402 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A369402 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} binomial(3*n+k+2,k) * binomial(2*n+2,n-3*k).
%F A369402 a(n) = (1/(n+1)) * [x^n] ( (1+x)^2 / (1-x^3)^3 )^(n+1). - _Seiichi Manyama_, Feb 16 2024
%o A369402 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x/(1+x)^2*(1-x^3)^3)/x)
%o A369402 (PARI) a(n, s=3, t=3, u=2) = sum(k=0, n\s, binomial(t*(n+1)+k-1, k)*binomial(u*(n+1), n-s*k))/(n+1);
%Y A369402 Cf. A369300, A370217.
%K A369402 nonn
%O A369402 0,2
%A A369402 _Seiichi Manyama_, Jan 22 2024