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 A113678 #3 Mar 30 2012 18:59:12
%S A113678 1,0,1,2,0,1,2,2,0,1,6,2,2,0,1,10,6,2,2,0,1,22,10,6,2,2,0,1,42,22,10,
%T A113678 6,2,2,0,1,86,42,22,10,6,2,2,0,1,170,86,42,22,10,6,2,2,0,1,342,170,86,
%U A113678 42,22,10,6,2,2,0,1,682,342,170,86,42,22,10,6,2,2,0,1,1366,682,342,170,86
%N A113678 Sequence array for A078008.
%C A113678 Row sums are A001045(n+1). Diagonal sums are A053088. Inverse is A113680.
%F A113678 Riordan array ((1-x)/(1-x-2x^2), x); Number triangle T(n, k)=if(k<=n, (2^(n-k)+2(-1)^(n-k))/3, 0); T(n, k)=sum{i=0..n, C(n-i, k)C(k, n-i)(2^i+2(-1)^i)/3}.
%e A113678 Triangle begins
%e A113678 1;
%e A113678 0, 1;
%e A113678 2, 0, 1;
%e A113678 2, 2, 0, 1;
%e A113678 6, 2, 2, 0, 1;
%e A113678 10, 6, 2, 2, 0, 1;
%e A113678 22, 10, 6, 2, 2, 0, 1;
%K A113678 easy,nonn,tabl
%O A113678 0,4
%A A113678 _Paul Barry_, Nov 04 2005