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 A115268 #3 Mar 30 2012 18:59:13
%S A115268 1,1,1,1,2,1,1,2,2,1,2,2,3,2,2,2,3,3,3,3,2,2,4,4,4,4,4,2,2,4,5,5,5,5,
%T A115268 4,2,3,4,6,6,8,6,6,4,3,3,5,6,7,9,9,7,6,5,3,3,6,7,8,10,12,10,8,7,6,3,3,
%U A115268 6,8,9,11,13,13,11,9,8,6,3,4,6,9,10,14,14,16,14,14,10,9,6,4
%N A115268 Correlation triangle for floor((n+4)/4).
%C A115268 Row sums are A115269. Diagonal sums are A115270. T(2n,n) is A115271. T(2n,n)-T(2n,n-1) is 1,1,1,0,2,2,2,0,3,3,3,0,...
%F A115268 G.f.: (1+x+x^2+x^3)(1+xy+x^2*y^2+x^3*y^3)/((1-x^4)^2*(1-x^4*y^4)^2*(1-x^2*y)); Number triangle T(n, k)=sum{j=0..n, [j<=k]*floor((k-j+4)/4)*[j<=n-k]*floor((n-k-j+4)/4)}.
%e A115268 Triangle begins
%e A115268 1;
%e A115268 1,1;
%e A115268 1,2,1;
%e A115268 1,2,2,1;
%e A115268 2,2,3,2,2;
%e A115268 2,3,3,3,3,2;
%e A115268 2,4,4,4,4,4,2;
%e A115268 2,4,5,5,5,5,4,2;
%e A115268 3,4,6,6,8,6,6,4,3;
%e A115268 3,5,6,7,9,9,7,6,5,3;
%e A115268 3,6,7,8,10,12,10,8,7,6,3;
%e A115268 3,6,8,9,11,13,13,11,9,8,6,3;
%K A115268 easy,nonn,tabl
%O A115268 0,5
%A A115268 _Paul Barry_, Jan 18 2006