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 A101126 #6 Mar 30 2012 18:59:02
%S A101126 1,0,0,1,3,3,8,30,117,466,1960,8655,40391,200085,1051888,5844844,
%T A101126 34131049,208344660,1324262256,8743620525,59891078347,425216195191,
%U A101126 3126418416440,23778261543210,186815245299549,1513931016854598
%N A101126 Diagonal sums of a Chebyshev number triangle.
%C A101126 Diagonal sums of number triangle A101124.
%H A101126 <a href="/index/Ch#Cheby">Index entries for sequences related to Chebyshev polynomials.</a>
%F A101126 a(n)=sum{k=0..floor(n/2), if(k<n-k, T(n-2k, k), if(k=n-k, 1, 0))} where T(n, k)=(n/2)sum{j=0..floor(n/2), C(n-j, j)(-1)^j*(2k)^(n-2j)}.
%K A101126 easy,nonn
%O A101126 0,5
%A A101126 _Paul Barry_, Dec 02 2004