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 A027143 #10 Jul 11 2023 15:17:05
%S A027143 57,486,4117,34760,293086,2471917,20870169,176467252,1494672812,
%T A027143 12682766442,107814252502,918166760699,7832993240285,66936986352534,
%U A027143 572934789920969,4911478255448828,42165255645650628,362494201554529232,3120475613849051712,26895832224848130557
%N A027143 a(n) = Sum_{k=0..2n-3} T(n,k) * T(n,k+3), with T given by A027113.
%Y A027143 Cf. A027113.
%K A027143 nonn
%O A027143 3,1
%A A027143 _Clark Kimberling_
%E A027143 More terms from _Sean A. Irvine_, Oct 23 2019