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 A121422 #6 Mar 30 2012 18:36:58
%S A121422 1,3,15,118,1317,19311,352636,7722840,197354133,5764942816,
%T A121422 189460961985,6917588290044,277765971072770,12163275845132298,
%U A121422 576793897136731632,29444368084753254610,1609805318425385690712,93843785859803533422675
%N A121422 Column 1 of triangle A121420.
%C A121422 Also column 2 of square array A136737.
%C A121422 A121420 is the matrix cube of triangle A121412; row n of triangle T=A121412 equals row (n-1) of T^(n+1) with an appended '1'.
%o A121422 (PARI) {a(n)=local(A=Mat(1), B); for(m=1, n+2, B=matrix(m, m); for(i=1, m, for(j=1, i, if(j==i, B[i,j]=1, B[i, j]=(A^i)[i-1, j]); )); A=B); return((A^3)[n+2, 2])}
%Y A121422 Cf. A121420 (triangle); other columns: A121421, A121423.
%Y A121422 Cf. A136737; A121413, A121417; A121427, A136741.
%K A121422 nonn
%O A121422 0,2
%A A121422 _Paul D. Hanna_, Aug 23 2006
%E A121422 Edited by _N. J. A. Sloane_, Oct 30 2008 at the suggestion of R. J. Mathar