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 A109246 #2 Mar 30 2012 18:59:08 %S A109246 1,-1,1,-2,-2,1,0,-1,-3,1,0,2,1,-4,1,0,0,3,4,-5,1,0,0,-2,2,8,-6,1,0,0, %T A109246 0,-5,-2,13,-7,1,0,0,0,2,-7,-10,19,-8,1,0,0,0,0,7,-5,-23,26,-9,1,0,0, %U A109246 0,0,-2,14,5,-42,34,-10,1,0,0,0,0,0,-9,19,28,-68,43,-11,1,0,0,0,0,0,2,-23,14,70,-102,53,-12,1,0,0,0,0,0,0,11,-42,-14 %N A109246 Riordan array (1-x-2x^2,x(1-x)). %C A109246 Matrix inverse of A109244. Row sums are A109247. Diagonal sums are A109248. %e A109246 Rows begin %e A109246 1; %e A109246 -1,1; %e A109246 -2,-2,1; %e A109246 0,-1,-3,1; %e A109246 0,2,1,-4,1; %e A109246 0,0,3,4,-5,1 %K A109246 easy,sign,tabl %O A109246 0,4 %A A109246 _Paul Barry_, Jun 23 2005