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 A137961 #10 Mar 03 2018 13:53:03
%S A137961 1,1,5,20,105,575,3306,19760,121035,757230,4815530,31039402,202335855,
%T A137961 1331569725,8834918160,59035907480,396937508816,2683518356850,
%U A137961 18230570856710,124390574548960,852074529347120,5857453791938135
%N A137961 G.f. satisfies A(x) = 1 + x*(1 + x*A(x)^2)^5.
%H A137961 Vaclav Kotesovec, <a href="/A137961/b137961.txt">Table of n, a(n) for n = 0..400</a>
%F A137961 G.f.: A(x) = 1 + x*B(x)^5 where B(x) is the g.f. of A137960.
%F A137961 a(n) = Sum_{k=0..n-1} C(5*(n-k),k)/(n-k) * C(2*k,n-k-1) for n>0 with a(0)=1. - _Paul D. Hanna_, Jun 16 2009
%F A137961 a(n) ~ sqrt(5*s*(1-s)*(2-3*s) / ((36*s - 20)*Pi)) / (n^(3/2) * r^n), where r = 0.1354712934479194768810666044866029126617104117352... and s = 1.618016818966151244027202981456410137451426090894... are real roots of the system of equations s = 1 + r*(1 + r*s^2)^5, 10 * r^2 * s * (1 + r*s^2)^4 = 1. - _Vaclav Kotesovec_, Nov 22 2017
%o A137961 (PARI) {a(n)=local(A=1+x*O(x^n));for(i=0,n,A=1+x*(1+x*A^2)^5);polcoeff(A,n)}
%o A137961 (PARI) a(n)=if(n==0,1,sum(k=0,n-1,binomial(5*(n-k),k)/(n-k)*binomial(2*k,n-k-1))) \\ _Paul D. Hanna_, Jun 16 2009
%Y A137961 Cf. A137960, A137962; A137963, A137965, A137973.
%K A137961 nonn
%O A137961 0,3
%A A137961 _Paul D. Hanna_, Feb 26 2008