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 A369230 #10 Jan 17 2024 09:35:41
%S A369230 1,0,3,3,24,54,283,900,4098,15286,66555,268173,1156951,4852722,
%T A369230 21007605,90167059,393152058,1712432070,7524092134,33112353060,
%U A369230 146518404963,649861681966,2893369443183,12913307575722,57800647230933,259298148600504,1165967972216967
%N A369230 Expansion of (1/x) * Series_Reversion( x * (1-x)^3 / (1-x+x^2)^3 ).
%H A369230 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A369230 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} binomial(3*n+3,k) * binomial(n-k-1,n-2*k).
%o A369230 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*(1-x)^3/(1-x+x^2)^3)/x)
%o A369230 (PARI) a(n, s=2, 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 A369230 Cf. A366049, A369229.
%Y A369230 Cf. A369078.
%K A369230 nonn
%O A369230 0,3
%A A369230 _Seiichi Manyama_, Jan 17 2024