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 A371577 #16 Mar 30 2024 02:38:09
%S A371577 1,2,11,70,505,3910,31772,267280,2307982,20339946,182207333,
%T A371577 1654250474,15187764411,140767293560,1315349040350,12377806027892,
%U A371577 117200381305538,1115791797318548,10674418686087377,102563189093302366,989321056200478417
%N A371577 G.f. satisfies A(x) = ( 1 + x*A(x)^2 * (1 + x) )^2.
%F A371577 a(n) = Sum_{k=0..n} binomial(4*k+2,k) * binomial(k,n-k)/(2*k+1).
%F A371577 G.f.: A(x) = B(x)^2 where B(x) is the g.f. of A365178.
%o A371577 (PARI) a(n, r=2, s=1, t=4, u=0) = r*sum(k=0, n, binomial(t*k+u*(n-k)+r, k)*binomial(s*k, n-k)/(t*k+u*(n-k)+r));
%Y A371577 Cf. A001629, A052705, A371576, A371578.
%Y A371577 Cf. A365178.
%K A371577 nonn
%O A371577 0,2
%A A371577 _Seiichi Manyama_, Mar 28 2024