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 A371893 #8 Apr 11 2024 10:10:09
%S A371893 1,2,0,16,-32,336,-1472,10944,-63744,441088,-2866688,19772416,
%T A371893 -134832128,941381632,-6585720832,46607831040,-331406262272,
%U A371893 2373110628352,-17072541007872,123438375763968,-896088779128832,6530356893777920,-47752086733717504
%N A371893 G.f. A(x) satisfies A(x) = 1 + x/A(x)^2 * (1 + A(x)^4).
%F A371893 a(n) = (-1)^(n-1) * (1/n) * Sum_{k=0..n} binomial(n,k) * binomial(3*n-4*k-2,n-1) for n > 0.
%o A371893 (PARI) a(n) = if(n==0, 1, (-1)^(n-1)*sum(k=0, n, binomial(n, k)*binomial(3*n-4*k-2, n-1))/n);
%Y A371893 Cf. A364393, A364394, A364396, A364397, A366364.
%K A371893 sign
%O A371893 0,2
%A A371893 _Seiichi Manyama_, Apr 11 2024