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 A122431 #2 Mar 30 2012 18:59:15 %S A122431 1,3,1,3,3,1,1,3,3,1,0,1,3,3,1,0,0,1,3,3,1,0,0,0,1,3,3,1,0,0,0,0,1,3, %T A122431 3,1,0,0,0,0,0,1,3,3,1,0,0,0,0,0,0,1,3,3,1,0,0,0,0,0,0,0,1 %N A122431 Riordan array ((1+x)^3,x). %C A122431 Row sums are A115291. Diagonal sums are A113311. Inverse is A122432. Sequence array for C(3,n). %F A122431 Number triangle T(n,k)=C(3,n-k) %e A122431 Triangle begins %e A122431 1, %e A122431 3,1, %e A122431 3,3,1, %e A122431 1,3,3,1, %e A122431 0,1,3,3,1, %e A122431 0,0,1,3,3,1, %e A122431 0,0,0,1,3,3,1, %e A122431 0,0,0,0,1,3,3,1 %K A122431 easy,nonn,tabl %O A122431 0,2 %A A122431 _Paul Barry_, Sep 04 2006