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 A117377 #3 Mar 30 2012 18:59:14 %S A117377 1,-4,1,0,-5,1,0,4,-6,1,0,0,9,-7,1,0,0,-4,15,-8,1,0,0,0,-13,22,-9,1,0, %T A117377 0,0,4,-28,30,-10,1,0,0,0,0,17,-50,39,-11,1,0,0,0,0,-4,45,-80,49,-12, %U A117377 1,0,0,0,0,0,-21,95,-119,60,-13,1 %N A117377 Riordan array (1-4x,x(1-x)). %C A117377 Row sums are A117378. Diagonal sums are A117379. Inverse is A117380. %F A117377 Number triangle T(n,k)=(-1)^(n-k)(C(k,n-k)+4*C(k, n-k-1)) %e A117377 Triangle begins %e A117377 1, %e A117377 -4, 1, %e A117377 0, -5, 1, %e A117377 0, 4, -6, 1, %e A117377 0, 0, 9, -7, 1, %e A117377 0, 0, -4, 15, -8, 1, %e A117377 0, 0, 0, -13, 22, -9, 1, %e A117377 0, 0, 0, 4, -28, 30, -10, 1 %K A117377 easy,sign,tabl %O A117377 0,2 %A A117377 _Paul Barry_, Mar 10 2006