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 A121416 #3 Mar 30 2012 18:36:58
%S A121416 1,2,1,7,2,1,43,9,2,1,403,69,11,2,1,5188,769,101,13,2,1,85569,11346,
%T A121416 1305,139,15,2,1,1725291,208914,21745,2043,183,17,2,1,41145705,
%U A121416 4613976,443329,37971,3015,233,19,2,1,1133047596,118840164,10679494,850260
%N A121416 Matrix square of triangle A121412.
%C A121416 Row n of triangle T=A121412 equals row (n-1) of T^(n+1) with an appended '1'.
%e A121416 Triangle begins:
%e A121416 1;
%e A121416 2, 1;
%e A121416 7, 2, 1;
%e A121416 43, 9, 2, 1;
%e A121416 403, 69, 11, 2, 1;
%e A121416 5188, 769, 101, 13, 2, 1;
%e A121416 85569, 11346, 1305, 139, 15, 2, 1;
%e A121416 1725291, 208914, 21745, 2043, 183, 17, 2, 1;
%e A121416 41145705, 4613976, 443329, 37971, 3015, 233, 19, 2, 1;
%e A121416 1133047596, 118840164, 10679494, 850260, 61860, 4253, 289, 21, 2, 1;
%o A121416 (PARI) {T(n, k)=local(A=Mat(1), B); for(m=1, n+1, 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^2)[n+1, k+1])}
%Y A121416 Cf. A121412, A121420; A101479; columns: A121417, A121418, A121419.
%K A121416 nonn,tabl
%O A121416 0,2
%A A121416 _Paul D. Hanna_, Aug 22 2006