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 A115283 #5 Jun 13 2015 00:52:03
%S A115283 1,3,6,13,18,27,37,48,60,76,90,108,127,147,168,193,216,243,271,300,
%T A115283 330,364,396,432,469,507,546,589,630,675,721,768,816,868,918,972,1027,
%U A115283 1083,1140,1201,1260,1323,1387,1452,1518,1588,1656,1728,1801
%N A115283 Diagonal sums of correlation triangle for 3-2*0^n.
%C A115283 Diagonal sums of number triangle A115282.
%H A115283 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,0,-1,-1,1).
%F A115283 G.f.: (1+2x)(1+2x^2)/((1-x)(1-x^2)(1-x^3)); a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, [j<=k]*(3-2*0^(k-j))*[j<=n-2k]*(3-2*0^(n-2k-j))}}.
%K A115283 easy,nonn
%O A115283 0,2
%A A115283 _Paul Barry_, Jan 19 2006