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 A107250 #3 Mar 30 2012 18:59:07
%S A107250 1,1,2,3,5,9,16,30,54,104,191,372,692,1357,2550,5021,9508,18773,35766,
%T A107250 70755,135461,268365,515849,1023092,1973159,3916831,7575470,15048428,
%U A107250 29175431,57990158,112665488,224048847,436089113,867581269,1691392152
%N A107250 Diagonal sums of number array A107249.
%F A107250 a(n)=sum{k=0..floor(n/2), C(floor((2n-3k-2)/2), floor((n-2k)/2))}
%K A107250 easy,nonn
%O A107250 0,3
%A A107250 _Paul Barry_, May 14 2005