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 A369486 #12 Jan 24 2024 08:00:24
%S A369486 1,1,4,15,67,314,1547,7865,41004,217953,1176832,6436676,35587416,
%T A369486 198569471,1116741601,6323669519,36024382515,206315985386,
%U A369486 1187205083042,6860598312545,39797882898452,231666709974264,1352813494962672,7922553881534274,46520280837291427
%N A369486 Expansion of (1/x) * Series_Reversion( x / (1-x) * (1-x-x^2)^2 ).
%H A369486 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A369486 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} binomial(2*n+k+1,k) * binomial(2*n-k,n-2*k).
%o A369486 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x/(1-x)*(1-x-x^2)^2)/x)
%o A369486 (PARI) a(n, s=2, t=2, u=1) = 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 A369486 Cf. A368957, A368961, A368965, A368967.
%K A369486 nonn
%O A369486 0,3
%A A369486 _Seiichi Manyama_, Jan 24 2024