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 A371518 #9 Mar 26 2024 11:14:53
%S A371518 1,2,11,72,525,4104,33647,285526,2486809,22103726,199697284,
%T A371518 1828472914,16929944932,158246198836,1491210732346,14151603542612,
%U A371518 135130396860130,1297381593071890,12516650939119421,121281286192026308,1179769340479567499
%N A371518 G.f. A(x) satisfies A(x) = (1 + x*A(x)^2 / (1-x))^2.
%F A371518 a(n) = 2 * Sum_{k=0..n} binomial(n-1,n-k) * binomial(4*k+1,k)/(3*k+2).
%F A371518 G.f.: A(x) = B(x)^2 where B(x) is the g.f. of A349331.
%o A371518 (PARI) a(n) = 2*sum(k=0, n, binomial(n-1, n-k)*binomial(4*k+1, k)/(3*k+2));
%Y A371518 Cf. A349331, A371483, A371517.
%Y A371518 Cf. A270386, A371523.
%K A371518 nonn
%O A371518 0,2
%A A371518 _Seiichi Manyama_, Mar 26 2024