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 A363819 #11 Oct 18 2023 09:58:29
%S A363819 1,4,1,38,-193,1697,-14298,127836,-1175835,11078851,-106354266,
%T A363819 1036575329,-10230191020,102031153812,-1026763493315,10412602349343,
%U A363819 -106308046392516,1091783632303656,-11271378486953873,116907289944782853,-1217649336037820058
%N A363819 G.f. satisfies A(x) = (1 + x/A(x)^2)/(1 - x)^3.
%F A363819 a(n) = (-1)^(n-1) * Sum_{k=0..n} binomial(3*k-1,k) * binomial(3*(2*k-1),n-k)/(3*k-1).
%o A363819 (PARI) a(n) = (-1)^(n-1)*sum(k=0, n, binomial(3*k-1, k)*binomial(3*(2*k-1), n-k)/(3*k-1));
%Y A363819 Cf. A366364, A363818.
%K A363819 sign
%O A363819 0,2
%A A363819 _Seiichi Manyama_, Oct 18 2023