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 A136229 #2 Mar 30 2012 18:37:08
%S A136229 1,4,24,198,2116,28052,446560,8325700,178284892,4317391240,
%T A136229 116757568072,3489919886180,114304360656596,4072431454706374,
%U A136229 156845310426959972,6494800764749659199,287796117221639178946,13590112496057829388516
%N A136229 Column 1 of triangle A136228; also equals column 3 of square array A136217.
%o A136229 (PARI) {a(n)=local(P=Mat(1),U=Mat([1,0;1,1]),PShR);if(n>0,for(i=0,n+1, PShR=matrix(#P,#P, r,c, if(r>=c,if(r==c,1,if(c==1,0,P[r-1,c-1]))));U=P*PShR^2; U=matrix(#P+1, #P+1, r,c, if(r>=c, if(r<#P+1,U[r,c], if(c==1,(P^3)[ #P,1],(P^(3*c-1))[r-c+1,1])))); P=matrix(#U, #U, r,c, if(r>=c, if(r<#R,P[r,c], (U^c)[r-c+1,1])))));U[n+2,2]}
%Y A136229 Cf. A136228, A136217; A136221.
%K A136229 nonn
%O A136229 0,2
%A A136229 _Paul D. Hanna_, Jan 28 2008