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 A369502 #8 Jan 25 2024 07:49:32
%S A369502 1,6,47,420,4059,41316,436345,4737018,52535950,592667532,6779699073,
%T A369502 78458218746,916886214115,10805128064100,128260666769895,
%U A369502 1532180536574580,18405744106135914,222204347510440092,2694506677864591810,32804976554127379680,400837173223351237295
%N A369502 Expansion of (1/x) * Series_Reversion( x / ((1+x)^2+x)^2 ).
%H A369502 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A369502 a(n) = (1/(n+1)) * Sum_{k=0..n} binomial(2*n+2,k) * binomial(4*n-2*k+4,n-k).
%o A369502 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x/((1+x)^2+x)^2)/x)
%o A369502 (PARI) a(n) = sum(k=0, n, binomial(2*n+2, k)*binomial(4*n-2*k+4, n-k))/(n+1);
%Y A369502 Cf. A369503, A369504.
%Y A369502 Cf. A003645, A369505.
%K A369502 nonn
%O A369502 0,2
%A A369502 _Seiichi Manyama_, Jan 25 2024