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 A122440 #2 Mar 30 2012 18:59:18 %S A122440 1,-2,1,4,-4,1,-16,16,-6,1,80,-80,32,-8,1,-448,448,-184,52,-10,1,2688, %T A122440 -2688,1120,-336,76,-12,1,-16896,16896,-7104,2208,-544,104,-14,1, %U A122440 109824 %N A122440 Riordan array ((3-sqrt(1+8x))/2, (sqrt(1+8x)-1)/4). %C A122440 Inverse of A122438. Row sums are A122441. %e A122440 Triangle begins %e A122440 1, %e A122440 -2, 1, %e A122440 4, -4, 1, %e A122440 -16, 16, -6, 1, %e A122440 80, -80, 32, -8, 1, %e A122440 -448, 448, -184, 52, -10, 1, %e A122440 2688, -2688, 1120, -336, 76, -12, 1 %K A122440 easy,sign,tabl %O A122440 0,2 %A A122440 _Paul Barry_, Sep 05 2006