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 A372012 #13 Apr 19 2024 10:31:21
%S A372012 1,-1,3,-5,17,-31,119,-211,937,-1483,8015,-10187,73369,-62193,713907,
%T A372012 -234857,7358657,1881661,80117735,69295469,917837521,1334044075,
%U A372012 11006114883,21830065899,137275956089,333858963899,1769128762419,4940496514271,23409778504937
%N A372012 G.f. A(x) satisfies A(x) = 1/( 1 + x*(1 - 4*x*A(x))^(1/2) ).
%F A372012 a(n) = (-1)^n * Sum_{k=0..n} 4^(n-k) * binomial(n,k) * binomial(k/2,n-k)/(n-k+1).
%o A372012 (PARI) a(n) = (-1)^n*sum(k=0, n, 4^(n-k)*binomial(n, k)*binomial(k/2, n-k)/(n-k+1));
%Y A372012 Cf. A166587, A362154, A372013.
%K A372012 sign
%O A372012 0,3
%A A372012 _Seiichi Manyama_, Apr 19 2024