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 A124542 #3 Mar 30 2012 18:37:01
%S A124542 1,2,7,26,107,486,2398,12668,70863,416304,2552490,16254406,107095090,
%T A124542 727834866,5089682472,36548625188,269065010063,2027942075946,
%U A124542 15630423416331,123079853443384,989356860469923,8112792202324232
%N A124542 Row 2 of rectangular table A124540; equals the self-convolution of A124532 (row 2 of table A124530).
%C A124542 In table A124540, the g.f. of row n, R_n(y), simultaneously satisfies: R_n(y) = [ Sum_{k>=0} y^k*R_k(y)^n ]^n for n>=0.
%o A124542 (PARI) {a(n)=local(R);R=vector(n+3,r,vector(n+3,c,1)); for(i=0,n+2,for(r=0,n+2,R[r+1]=Vec(sum(c=0,n,x^c*Ser(R[c+1])^(r*c)+O(x^(n+1)))))); Vec(Ser(R[3])^2+O(x^(n+1)))[n+1]}
%Y A124542 Cf. A124532; A124540 (table); other rows: A124531, A124543, A124544, A124545, A124546.
%K A124542 nonn
%O A124542 0,2
%A A124542 _Paul D. Hanna_, Nov 05 2006