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 A371545 #9 Mar 27 2024 08:48:47
%S A371545 1,2,7,36,209,1312,8663,59298,416961,2993790,21857208,161768154,
%T A371545 1210949944,9152366596,69745701746,535304423948,4134240993874,
%U A371545 32105769989714,250551371644825,1963871015580984,15454014753626079,122044659649929546,966951068210379441
%N A371545 G.f. A(x) satisfies A(x) = (1 + x*A(x)^2 / (1+x))^2.
%F A371545 a(n) = 2 * Sum_{k=0..n} (-1)^(n-k) * binomial(n-1,n-k) * binomial(4*k+2,k)/(4*k+2).
%o A371545 (PARI) a(n) = 2*sum(k=0, n, (-1)^(n-k)*binomial(n-1, n-k)*binomial(4*k+2, k)/(4*k+2));
%Y A371545 Cf. A317133, A371495, A371543.
%Y A371545 Cf. A371518.
%K A371545 nonn
%O A371545 0,2
%A A371545 _Seiichi Manyama_, Mar 26 2024