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 A368963 #21 Sep 20 2024 12:27:39
%S A368963 1,3,18,130,1044,8949,80201,742365,7042215,68103156,668913195,
%T A368963 6654654240,66916523202,679039933050,6944796387690,71512538784330,
%U A368963 740800257667236,7714659988543299,80719544259082000,848155028673449400,8945940728543188656
%N A368963 Expansion of (1/x) * Series_Reversion( x * (1-x-x^2)^3 ).
%H A368963 Seiichi Manyama, <a href="/A368963/b368963.txt">Table of n, a(n) for n = 0..952</a>
%H A368963 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A368963 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} binomial(3*n+k+2,k) * binomial(4*n-k+2,n-2*k).
%F A368963 G.f.: B(x)^3, where B(x) is the g.f. of A365182. - _Seiichi Manyama_, Sep 20 2024
%o A368963 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*(1-x-x^2)^3)/x)
%o A368963 (PARI) a(n, s=2, t=3, u=0) = sum(k=0, n\s, binomial(t*(n+1)+k-1, k)*binomial((t+u+1)*(n+1)-(s-1)*k-2, n-s*k))/(n+1);
%Y A368963 Cf. A368964, A368971.
%Y A368963 Cf. A365182.
%K A368963 nonn
%O A368963 0,2
%A A368963 _Seiichi Manyama_, Jan 10 2024