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 A027149 #7 Oct 24 2019 16:01:16 %S A027149 1,10,42,352,1360,11616,43680,381952,1416960,12620800,46441472, %T A027149 419512320,1535352832,14021353472,51117465600,470886645760, %U A027149 1711716106240,15879295991808,57592095965184,537381547540480,1945481074704384 %N A027149 a(n) = A027144(2n-1, n-2). %K A027149 nonn %O A027149 2,2 %A A027149 _Clark Kimberling_