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 A108149 #4 Mar 30 2012 17:28:32 %S A108149 1,-1,1,0,0,1,0,1,-1,1,1,0,1,0,1,-1,2,-1,2,-1,1,1,0,3,0,2,0,1,-1,4,-3, %T A108149 5,-2,3,-1,1,3,0,6,0,6,0,3,0,1,-3,9,-6,12,-6,9,-3,4,-1,1,6,0,15,0,15, %U A108149 0,10,0,4,0,1,-6,21,-15,30,-15,25,-10,14,-4,5,-1,1,15,0,36,0,40,0,29,0,15,0,5,0,1,-15,51,-36,76,-40,69,-29,44,-15,20,-5 %N A108149 Triangle T(n,k), 0<=k<=n, read by rows, defined by: T(0,0)=1,T(n,k)= 0 if n<k, T(n,k) = (-1)^n*T(n-1,k) + T(n-1,k-1) + T(n-1,k+1). %C A108149 The n-th row sum = A005213(n). %Y A108149 Cf. A005213. %K A108149 sign,tabl %O A108149 0,17 %A A108149 _Gerald McGarvey_, Jun 05 2005