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 A363818 #19 Oct 18 2023 11:35:40
%S A363818 1,3,-1,24,-125,924,-6895,54181,-438737,3639655,-30769033,264122781,
%T A363818 -2296010693,20171456222,-178818115155,1597550237324,-14369097515939,
%U A363818 130010781029079,-1182520161325459,10806114831458755,-99163805247182631,913441732959868748
%N A363818 G.f. satisfies A(x) = (1 + x/A(x)^2)/(1 - x)^2.
%F A363818 a(n) = (-1)^(n-1) * Sum_{k=0..n} binomial(3*k-1,k) * binomial(2*(2*k-1),n-k)/(3*k-1).
%o A363818 (PARI) a(n) = (-1)^(n-1)*sum(k=0, n, binomial(3*k-1, k)*binomial(2*(2*k-1), n-k)/(3*k-1));
%Y A363818 Cf. A162477, A363816, A364629, A364630.
%Y A363818 Cf. A363819, A366364.
%K A363818 sign
%O A363818 0,2
%A A363818 _Seiichi Manyama_, Oct 18 2023