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 A181656 #5 Sep 29 2018 18:47:32 %S A181656 1,0,1,1,1,1,0,0,0,1,0,0,1,1,1,0,0,0,0,0,1,0,0,0,0,1,1,1,0,0,0,0,0,0, %T A181656 0,1,0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,1,1,1 %N A181656 Generalized (conditional) Riordan array with k-th column generated by x^k*(1+x^2) if k mod 2 = 0, x^k*(1+x) otherwise. %C A181656 A181657 is an eigentriangle for this triangle. %e A181656 Triangle begins %e A181656 1; %e A181656 0, 1; %e A181656 1, 1, 1; %e A181656 0, 0, 0, 1; %e A181656 0, 0, 1, 1, 1; %e A181656 0, 0, 0, 0, 0, 1; %e A181656 0, 0, 0, 0, 1, 1, 1; %e A181656 0, 0, 0, 0, 0, 0, 0, 1; %e A181656 0, 0, 0, 0, 0, 0, 1, 1, 1; %e A181656 0, 0, 0, 0, 0, 0, 0, 0, 0, 1; %e A181656 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1; %e A181656 Production matrix begins %e A181656 0, 1; %e A181656 1, 1, 1; %e A181656 -1, -2, -1, 1; %e A181656 0, 0, 1, 1, 1; %e A181656 1, 2, 0, -2, -1, 1; %e A181656 0, 0, 0, 0, 1, 1, 1; %e A181656 -1, -2, 0, 2, 0, -2, -1, 1; %e A181656 0, 0, 0, 0, 0, 0, 1, 1, 1; %e A181656 1, 2, 0, -2, 0, 2, 0, -2, -1, 1; %e A181656 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1; %K A181656 easy,nonn,tabl %O A181656 0,1 %A A181656 _Paul Barry_, Nov 03 2010