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 A132693 #2 Mar 30 2012 18:37:04
%S A132693 1,1,-3,22,-250,3810,-72492,1649634,-43626510,1313526375,-44332221175,
%T A132693 1657043432088,-67929461003560,3029864359322346,-146058681728370600,
%U A132693 7566706624571096610,-419220650458638848514,24733868801871384287055,-1548237182318766914543100
%N A132693 Column 2 of triangle A132690.
%C A132693 Triangle T=A132690 is generated from negative powers of itself such that row n+1 of T = row n of T^(-n) with appended '1' for n>=0 with T(0,0)=1.
%o A132693 (PARI) {a(n)=local(A=Mat(1), B); for(m=1, n+3, B=matrix(m, m); for(i=1, m, for(j=1, i, if(j==i, B[i, j]=1, B[i, j]=(A^(-(i-2)))[i-1, j]); )); A=B); return( ((A)[n+3,3]))}
%Y A132693 Cf. A132690; A132691, A132692, A132694.
%K A132693 sign
%O A132693 0,3
%A A132693 _Paul D. Hanna_, Aug 25 2007