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 A027289 #8 Oct 26 2019 23:08:52
%S A027289 1,3,18,55,264,847,3744,12465,52868,180895,749220,2617173,10680656,
%T A027289 37915317,153240864,551019963,2212417314,8038946075,32129224712,
%U A027289 117758845827,469105048654,1731917060158,6882935960496,25569740611270,101442831429264,378875492015643
%N A027289 a(n) = Sum_{k=0..floor(n/2)-1} T(n,k) * T(n,k+2), with T given by A026009.
%K A027289 nonn
%O A027289 2,2
%A A027289 _Clark Kimberling_
%E A027289 More terms from _Sean A. Irvine_, Oct 26 2019