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 A027123 #7 Oct 23 2019 20:35:03 %S A027123 1,4,13,44,145,467,1475,4588,14099,42919,129685,389578,1164909, %T A027123 3470513,10309111,30551216,90368547,266900346,787325255,2320267136, %U A027123 6832609927,20108081817,59149096985,173927024292,511290023185 %N A027123 a(n) = A027113(n, 2n-5). %K A027123 nonn %O A027123 3,2 %A A027123 _Clark Kimberling_