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 A371580 #14 Mar 30 2024 02:37:51
%S A371580 1,2,15,126,1211,12544,136668,1543696,17914325,212308682,2558783193,
%T A371580 31265632206,386430721728,4822586987324,60686262591525,
%U A371580 769167948066520,9810280980482827,125819903217235130,1621648696092783746,20993171222948561746,272848383910348808089
%N A371580 G.f. satisfies A(x) = ( 1 + x*A(x)^(5/2) * (1 + x)^2 )^2.
%F A371580 a(n) = 2 * Sum_{k=0..n} binomial(5*k+2,k) * binomial(2*k,n-k)/(5*k+2).
%o A371580 (PARI) a(n, r=2, s=2, t=5, u=0) = r*sum(k=0, n, binomial(t*k+u*(n-k)+r, k)*binomial(s*k, n-k)/(t*k+u*(n-k)+r));
%Y A371580 Cf. A371578, A371585.
%K A371580 nonn
%O A371580 0,2
%A A371580 _Seiichi Manyama_, Mar 28 2024