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 A049709 #8 Aug 07 2021 00:07:59
%S A049709 2,3,4,7,9,14,18,26,33,45,52,70,85,102,120,148,168,202,229,265,301,
%T A049709 349,386,444,497,554,608,682,738,819,894,986,1078,1178,1263,1383,1499,
%U A049709 1620,1725,1870,1989,2149,2289
%N A049709 a(n) = (1/2) * Sum_{i=0..n} T(i,n-i), array T as in A049704.
%K A049709 nonn
%O A049709 3,1
%A A049709 _Clark Kimberling_