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 A158839 #2 Mar 30 2012 18:37:16
%S A158839 1,4,34,412,6325,116372,2483706,60168736,1628677692,48672911296,
%T A158839 1590752204044,56418074957840,2157411204773415,88464995576660084,
%U A158839 3871611011946560294,180101399407072883012,8873328068327122625596
%N A158839 Column 3 of triangle A158835.
%C A158839 Triangle A158835 transforms diagonals in the array A158825 of coefficients of successive iterations of x*C(x) where C(x) is the Catalan function (A000108).
%o A158839 (PARI) {a(n)=local(F=x, CAT=serreverse(x-x^2+x*O(x^(n+5))),M,N,P);M=matrix(n+5, n+5, r, c, F=x; for(i=1, r+c-2, F=subst(F, x, CAT)); polcoeff(F, c)); N=matrix(n+4, n+4, r, c, M[r, c]); P=matrix(n+4, n+4, r, c, M[r+1, c]); (P~*N~^-1)[n+4,4]}
%Y A158839 Cf. A158835, A158836, A158837, A158836, A158840.
%K A158839 nonn
%O A158839 0,2
%A A158839 _Paul D. Hanna_, Mar 28 2009