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 A367031 #9 Nov 02 2023 10:40:03
%S A367031 1,1,1,-1,-10,-33,-55,65,842,3230,6137,-6631,-102166,-421705,-864225,
%T A367031 795615,14526042,63072042,136736102,-102140350,-2256842380,
%U A367031 -10210904245,-23195817445,13298317815,371005984450,1740942920122,4120912606657,-1666840127743
%N A367031 G.f. satisfies A(x) = 1 + x*A(x)^2 - x^2*A(x)^4.
%F A367031 a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(2*n,k) * binomial(2*n-k,n-2*k) / (n+k+1).
%o A367031 (PARI) a(n) = sum(k=0, n\2, (-1)^k*binomial(2*n, k)*binomial(2*n-k, n-2*k)/(n+k+1));
%Y A367031 Cf. A082582, A367032.
%Y A367031 Cf. A006605.
%K A367031 sign
%O A367031 0,5
%A A367031 _Seiichi Manyama_, Nov 02 2023