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 A117198 #3 Mar 30 2012 18:59:14 %S A117198 1,1,1,1,0,1,0,1,0,1,0,0,0,0,1,0,1,1,0,0,1,0,0,0,0,0,0,1,0,0,0,1,0,0, %T A117198 0,1,0,0,1,0,0,0,0,0,1,0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0, %U A117198 0,1,0,1,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,1 %N A117198 Generalized Riordan array (1,x)+(x,x^2)+(x^2,x^3). %C A117198 Row sums are A083039. Diagonal sums are A117199. Inverse is A117200. %F A117198 Number triangle T(n,k)=if(n=k,1,0) OR if(n=2k+1,1,0) OR if(n=3k+2,1,0). %e A117198 Triangle begins %e A117198 1, %e A117198 1, 1, %e A117198 1, 0, 1, %e A117198 0, 1, 0, 1, %e A117198 0, 0, 0, 0, 1, %e A117198 0, 1, 1, 0, 0, 1, %e A117198 0, 0, 0, 0, 0, 0, 1, %e A117198 0, 0, 0, 1, 0, 0, 0, 1, %e A117198 0, 0, 1, 0, 0, 0, 0, 0, 1, %e A117198 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, %e A117198 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 %K A117198 easy,nonn,tabl %O A117198 0,1 %A A117198 _Paul Barry_, Mar 02 2006