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 A122919 #2 Mar 30 2012 18:59:18 %S A122919 1,1,1,3,3,1,9,10,5,1,28,34,21,7,1,90,117,83,36,9,1,297,407,319,164, %T A122919 55,11,1,1001,1430,1209,702,285,78,13,1,3432,5070,4550,2898,1350,454, %U A122919 105,15,1,11934,18122,17068,11696,6052 %N A122919 Inverse of Riordan array (1/(1+x+x^2),x/(1+x)^2). %C A122919 Row sums are A097613. Diagonal sums are A122920. Inverse of A122917. %F A122919 Riordan array ((1-3x+2x^2-(1-x)sqrt(1-4x))/(2x^2),(1-2x-sqrt(1-4x))/(2x)) %e A122919 Triangle begins %e A122919 1, %e A122919 1, 1, %e A122919 3, 3, 1, %e A122919 9, 10, 5, 1, %e A122919 28, 34, 21, 7, 1, %e A122919 90, 117, 83, 36, 9, 1, %e A122919 297, 407, 319, 164, 55, 11, 1, %e A122919 1001, 1430, 1209, 702, 285, 78, 13, 1 %K A122919 easy,nonn,tabl %O A122919 0,4 %A A122919 _Paul Barry_, Sep 19 2006