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 A366273 #12 Oct 06 2023 08:33:44
%S A366273 1,1,9,81,849,9681,116601,1459809,18809121,247782369,3322209001,
%T A366273 45187029809,621970864241,8647376531249,121261376439641,
%U A366273 1713085987837889,24358211622230081,348325689458584769,5006342381846708681,72279683684984063249,1047789195353379807121
%N A366273 G.f. A(x) satisfies A(x) = 1 + x*(1 + x)^4*A(x)^5.
%F A366273 a(n) = Sum_{k=0..n} binomial(4*k,n-k) * binomial(5*k,k)/(4*k+1).
%o A366273 (PARI) a(n) = sum(k=0, n, binomial(4*k, n-k)*binomial(5*k, k)/(4*k+1));
%Y A366273 Cf. A052709, A366221, A366272.
%Y A366273 Cf. A366268.
%K A366273 nonn
%O A366273 0,3
%A A366273 _Seiichi Manyama_, Oct 06 2023