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 A104447 #6 Jun 13 2017 01:29:46 %S A104447 1,2,5,13,39,139,587,2897,16462,106301,771313,6228073,55494336, %T A104447 541651873,5753940704,66147591142,818802488476,10864622564915, %U A104447 153914784829775,2319599022540318,37068215129072522,626279667948552452 %N A104447 Column 1 of triangular matrix A104446. %C A104447 A104446 equals the square of triangular matrix A104445, read by rows, where X=A104445 satisfies: SHIFT_LEFT_UP(X) = X^2 - X + I. %F A104447 a(n) = A091352(n-1) + A091353(n-1). %o A104447 (PARI) a(n)=local(A=Mat(1),B);for(m=1,n+1,B=A^2-A+A^0; A=matrix(m+1,m+1);for(i=1,m+1, for(j=1,i, if(i<2 || j==i,A[i,j]=1,if(j==1,A[i,j]=1,A[i,j]=B[i-1,j-1]))))); return((A^2)[n+2,2]) %Y A104447 Cf. A104446, A091352, A091353. %K A104447 nonn %O A104447 0,2 %A A104447 _Paul D. Hanna_, Mar 08 2005