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 A147750 #2 Mar 30 2012 18:59:21 %S A147750 1,0,1,1,1,1,1,3,2,1,3,6,6,3,1,5,14,15,10,4,1,11,30,38,29,15,5,1,21, %T A147750 66,92,81,49,21,6,1,43,142,220,216,150,76,28,7,1,85,306,516,560,435, %U A147750 253,111,36,8,1 %N A147750 Riordan array ((1-x-x^2)/(1-x-2x^2), x(1-x)/(1-2x)). %C A147750 Row sums are A061646. A147750=A007318^-1*A147747. %e A147750 Triangle begins %e A147750 1, %e A147750 0, 1, %e A147750 1, 1, 1, %e A147750 1, 3, 2, 1, %e A147750 3, 6, 6, 3, 1, %e A147750 5, 14, 15, 10, 4, 1, %e A147750 11, 30, 38, 29, 15, 5, 1, %e A147750 21, 66, 92, 81, 49, 21, 6, 1 %K A147750 easy,nonn,tabl %O A147750 0,8 %A A147750 _Paul Barry_, Nov 11 2008