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 A366696 #9 Oct 17 2023 08:19:23
%S A366696 1,3,10,57,378,2730,20853,165592,1353297,11307168,96148149,829336122,
%T A366696 7238765532,63816716547,567425771478,5082596905629,45820260590481,
%U A366696 415423374916503,3785371205061825,34647928319586375,318419608552433190,2937021429784279707
%N A366696 G.f. satisfies A(x) = (1 + x)^2 + x*A(x)^3.
%F A366696 a(n) = Sum_{k=0..n} binomial(2*(2*k+1),n-k) * binomial(3*k,k)/(2*k+1).
%o A366696 (PARI) a(n) = sum(k=0, n, binomial(2*(2*k+1), n-k)*binomial(3*k, k)/(2*k+1));
%Y A366696 Cf. A366266, A366697.
%Y A366696 Cf. A364620.
%K A366696 nonn
%O A366696 0,2
%A A366696 _Seiichi Manyama_, Oct 16 2023