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 A137967 #10 Mar 03 2018 13:53:42
%S A137967 1,1,2,13,66,406,2602,17271,118444,829514,5914980,42791085,313277294,
%T A137967 2316793170,17281455882,129867946828,982293317064,7472406051744,
%U A137967 57132051350160,438797394096378,3383870656327576,26191385476141936
%N A137967 G.f. satisfies A(x) = 1 + x*(1 + x*A(x)^6)^2.
%H A137967 Vaclav Kotesovec, <a href="/A137967/b137967.txt">Table of n, a(n) for n = 0..400</a>
%F A137967 G.f.: A(x) = 1 + x*B(x)^2 where B(x) is the g.f. of A137968.
%F A137967 a(n) = Sum_{k=0..n-1} C(2*(n-k),k)/(n-k) * C(6*k,n-k-1) for n>0 with a(0)=1. - _Paul D. Hanna_, Jun 16 2009
%F A137967 a(n) ~ sqrt(2*s*(1-s)*(6-7*s) / ((132*s - 120)*Pi)) / (n^(3/2) * r^n), where r = 0.1201742080825038015263858974579392344239858277873... and s = 1.297009871974239150024579315539982910111693413337... are real roots of the system of equations s = 1 + r*(1 + r*s^6)^2, 12 * r^2 * s^5 * (1 + r*s^6) = 1. - _Vaclav Kotesovec_, Nov 22 2017
%o A137967 (PARI) {a(n)=local(A=1+x*O(x^n));for(i=0,n,A=1+x*(1+x*A^6)^2);polcoeff(A,n)}
%o A137967 (PARI) a(n)=if(n==0,1,sum(k=0,n-1,binomial(2*(n-k),k)/(n-k)*binomial(6*k,n-k-1))) \\ _Paul D. Hanna_, Jun 16 2009
%Y A137967 Cf. A137968, A137966; A137952, A137955, A137960.
%K A137967 nonn
%O A137967 0,3
%A A137967 _Paul D. Hanna_, Feb 26 2008