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 A047143 #4 Mar 30 2012 18:56:53 %S A047143 1,3,8,23,80,290,1010,3521,12934,48498,180020,666648,2512214,9569120, %T A047143 36408682,138417669,529685612,2038304708,7852427512,30259337658, %U A047143 116937868076,453269554872,1759337897040,6833437297968,26582114114294 %N A047143 T(n,n-1), array T as in A047140. %K A047143 nonn %O A047143 1,2 %A A047143 _Clark Kimberling_