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 A117568 #2 Mar 30 2012 18:59:14 %S A117568 1,0,1,-1,0,1,-1,-1,0,1,1,-1,-1,0,1,1,1,-1,-1,0,1,-1,1,1,-1,-1,0,1,-1, %T A117568 -1,1,1,-1,-1,0,1,1,-1,-1,1,1,-1,-1,0,1,1,1,-1,-1,1,1,-1,-1,0,1,-1,1, %U A117568 1,-1,-1,1,1,-1,-1,0,1,-1,-1,1,1,-1,-1,1,1,-1,-1,0,1,1,-1,-1,1,1,-1,-1,1,1,-1,-1,0,1 %N A117568 Riordan array ((1-x^3)/(1+x^2),x). %C A117568 Inverse of number triangle A117567. Row sums are A117569. Diagonal sums are A102560. %e A117568 Triangle begins %e A117568 1, %e A117568 0, 1, %e A117568 -1, 0, 1, %e A117568 -1, -1, 0, 1, %e A117568 1, -1, -1, 0, 1, %e A117568 1, 1, -1, -1, 0, 1, %e A117568 -1, 1, 1, -1, -1, 0, 1, %e A117568 -1, -1, 1, 1, -1, -1, 0, 1, %e A117568 1, -1, -1, 1, 1, -1, -1, 0, 1 %K A117568 easy,sign,tabl %O A117568 0,1 %A A117568 _Paul Barry_, Mar 29 2006