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 A026333 #4 Mar 30 2012 18:56:06 %S A026333 1,3,21,156,1221,9828,80579,669273,5612505,47416278,402953376, %T A026333 3440825160,29498259546,253737784446,2188855109385,18928808608996, %U A026333 164046653525181 %N A026333 a(n) = T(3n,n), where T is the array in A026323. %K A026333 nonn %O A026333 0,2 %A A026333 _Clark Kimberling_