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 A122891 #11 Mar 30 2012 18:36:59
%S A122891 1,1,3,28,1625,3247268,10649997137454,113423713055030979289411081,
%T A122891 12864938683278671740537137672878980378983810317967737
%N A122891 Column sums of triangle A122890.
%o A122891 (PARI) {A122890(n, k)=local(F=x+x^2, G=x+x*O(x^k)); if(n<0, 0, for(i=1, n, G=subst(F, x, G)); polcoeff(G, k, x))}
%o A122891 /* Takes first 2^m terms in column m of A122890 to compute a(m): */
%o A122891 {for(m=0,8,print1(polcoeff(sum(N=1,2^m,sum(n=0,2^m,A122890(n,N)*x^n)*(1-x)^N+O(x^12)),m),","))}
%Y A122891 Cf. A122890, A122888; A007018.
%K A122891 nonn
%O A122891 0,3
%A A122891 _Paul D. Hanna_, Sep 18 2006