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 A026151 #12 Sep 19 2019 19:14:17 %S A026151 1,1,2,4,12,32,89,246,685,1912,5355,15038,42339,119484,337935,957738, %T A026151 2719539,7736208,22044444,62916696,179841270,514793944,1475586687, %U A026151 4234989242,12169352003,35009302296,100826681530,290683486132,838873595124 %N A026151 a(n) = T(n,n), where T is the array in A026148. %Y A026151 Cf. A026148 %Y A026151 First differences of A026325 for n > 1. %K A026151 nonn %O A026151 0,3 %A A026151 _Clark Kimberling_ %E A026151 a(0)-a(1) inserted and a(20) corrected by _Sean A. Irvine_, Sep 18 2019