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 A366200 #25 Oct 04 2023 12:50:57
%S A366200 1,1,6,33,209,1425,10206,75751,577494,4495368,35582439,285524184,
%T A366200 2317387098,18990744137,156918815760,1305927563487,10936673012579,
%U A366200 92098612059051,779391530714589,6624730079900931,56532669993156696,484156547579505717,4159926573597719575
%N A366200 G.f. A(x) satisfies A(x) = 1 + x*(1 + x)^3*A(x)^3.
%F A366200 a(n) = Sum_{k=0..n} binomial(3*k,n-k) * binomial(3*k,k)/(2*k+1).
%o A366200 (PARI) a(n) = sum(k=0, n, binomial(3*k, n-k)*binomial(3*k, k)/(2*k+1));
%Y A366200 Cf. A073155, A366216.
%K A366200 nonn
%O A366200 0,3
%A A366200 _Seiichi Manyama_, Oct 04 2023