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 A026090 #5 Jun 23 2013 10:31:50 %S A026090 1,3,9,68,552,4524,37531,314280,2651418,22503384,191935926,1643789136, %T A026090 14126691568,121764645876,1052237509089,9113317001712,79084764081720, %U A026090 687489330917088,5985694255080435,52187865620386860,455587704842911596 %N A026090 a(n) = T(3n,n), where T is the array defined in A026082. %K A026090 nonn %O A026090 0,2 %A A026090 _Clark Kimberling_