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 A116948 #3 Mar 30 2012 18:59:14 %S A116948 1,0,1,2,0,1,1,2,0,1,0,1,2,0,1,2,0,1,2,0,1,1,2,0,1,2,0,1,0,1,2,0,1,2, %T A116948 0,1,2,0,1,2,0,1,2,0,1,1,2,0,1,2,0,1,2,0,1,0,1,2,0,1,2,0,1,2,0,1,2,0, %U A116948 1,2,0,1,2,0,1,2,0,1,1,2,0,1,2,0,1,2,0,1,2,0,1 %N A116948 Riordan array ((1+2x^2)/(1-x^3),x). %C A116948 Row sums are A117571. Diagonal sums are A117572. Inverse is A116949. %F A116948 Number triangle T(n,k)=2*J(L((n-k+2)/3))[k<=n] where L(j/p) is the Legendre symbol of j and p and J(n)=A001045(n) %e A116948 Triangle begins %e A116948 1, %e A116948 0, 1, %e A116948 2, 0, 1, %e A116948 1, 2, 0, 1, %e A116948 0, 1, 2, 0, 1, %e A116948 2, 0, 1, 2, 0, 1, %e A116948 1, 2, 0, 1, 2, 0, 1, %e A116948 0, 1, 2, 0, 1, 2, 0, 1, %e A116948 2, 0, 1, 2, 0, 1, 2, 0, 1 %K A116948 easy,nonn,tabl %O A116948 0,4 %A A116948 _Paul Barry_, Mar 29 2006