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 A366236 #10 Oct 05 2023 08:35:01
%S A366236 1,2,6,25,110,520,2566,13073,68244,363129,1962304,10739914,59411546,
%T A366236 331652408,1865903040,10569319231,60227702736,345015430415,
%U A366236 1985747398748,11477353063881,66590427901454,387685469752989,2264180109124196,13261401158297918
%N A366236 G.f. A(x) satisfies A(x) = 1 + x + x*(1 + x)^2*A(x)^2.
%F A366236 G.f.: 2*(1+x) / (1 + sqrt(1-4*x*(1+x)^3)).
%F A366236 a(n) = Sum_{k=0..n} binomial(3*k+1,n-k) * binomial(2*k,k)/(k+1).
%o A366236 (PARI) a(n) = sum(k=0, n, binomial(3*k+1, n-k)*binomial(2*k, k)/(k+1));
%Y A366236 Cf. A073157, A366237, A366238.
%Y A366236 Cf. A000108.
%K A366236 nonn
%O A366236 0,2
%A A366236 _Seiichi Manyama_, Oct 05 2023