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 A369232 #11 Jan 17 2024 09:35:33
%S A369232 1,0,0,3,3,3,33,72,120,583,1731,3888,13759,44775,119793,381220,
%T A369232 1250328,3682284,11455153,37174428,114947724,359381467,1157319135,
%U A369232 3663615552,11581104121,37220909916,119192219799,380580143110,1225279436706,3948906772872,12705801908002
%N A369232 Expansion of (1/x) * Series_Reversion( x * (1-x)^3 / (1-x+x^3)^3 ).
%H A369232 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A369232 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} binomial(3*n+3,k) * binomial(n-2*k-1,n-3*k).
%o A369232 (PARI) my(N=40, x='x+O('x^N)); Vec(serreverse(x*(1-x)^3/(1-x+x^3)^3)/x)
%o A369232 (PARI) a(n, s=3, t=3, u=3) = sum(k=0, n\s, binomial(t*(n+1), k)*binomial((u-t+1)*(n+1)-(s-1)*k-2, n-s*k))/(n+1);
%Y A369232 Cf. A366052, A369231.
%Y A369232 Cf. A369081.
%K A369232 nonn
%O A369232 0,4
%A A369232 _Seiichi Manyama_, Jan 17 2024