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 A119302 #4 Mar 30 2012 18:59:15 %S A119302 1,-3,1,0,-5,1,0,7,-7,1,0,-3,18,-9,1,0,0,-22,33,-11,1,0,0,13,-65,52, %T A119302 -13,1,0,0,-3,75,-140,75,-15,1,0,0,0,-51,238,-255,102,-17,1,0,0,0,19, %U A119302 -266,570,-418,133,-19,1,0,0,0,-3,196,-882,1155,-637,168,-21,1 %N A119302 Inverse of number triangle binomial(3n-k,n-k). %C A119302 Row sums are A119303. Inverse of A119301. %F A119302 Riordan array (1-3x,x(1-x)^2); Number triangle T(n,k)=(C(2k,n-k)+3*C(2k,n-k-1))(-1)^(n-k). %e A119302 Triangle begins %e A119302 1, %e A119302 -3, 1, %e A119302 0, -5, 1, %e A119302 0, 7, -7, 1, %e A119302 0, -3, 18, -9, 1, %e A119302 0, 0, -22, 33, -11, 1, %e A119302 0, 0, 13, -65, 52, -13, 1, %e A119302 0, 0, -3, 75, -140, 75, -15, 1 %K A119302 easy,sign,tabl %O A119302 0,2 %A A119302 _Paul Barry_, May 13 2006