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 A027140 #8 Oct 23 2019 22:08:03
%S A027140 1,3,12,57,264,1261,6141,30276,150853,758145,3836896,19534086,
%T A027140 99957904,513756551,2650822585,13724435509,71275344341,371177285715,
%U A027140 1937791196448,10139548682524,53165765660928,279301910804937
%N A027140 a(n) = Sum_{k=0..n} T(n,k) * T(n,n+k), with T given by A027113.
%K A027140 nonn
%O A027140 0,2
%A A027140 _Clark Kimberling_