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 A047139 #5 Mar 30 2012 18:56:53 %S A047139 1,2,9,48,261,1534,9319,56808,353362,2227380,14099553,89931668, %T A047139 577292621,3718701300,24047442913,156059054586,1015345651345, %U A047139 6621929417524,43283675452318,283439130488986,1859169844171611 %N A047139 T(2n,n), array T as in A047130. %K A047139 nonn %O A047139 0,2 %A A047139 _Clark Kimberling_. Definition revised Dec 08 2006