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 A129875 #5 Mar 30 2013 04:53:35 %S A129875 0,2,4,9,22,45,120,239 %N A129875 Sequence t_n arising in enumeration of arrays of directed blocks (see Quaintance reference for precise definition). %D A129875 Jocelyn Quaintance, Combinatoric Enumeration of Two-Dimensional Proper Arrays, Discrete Math., 307 (2007), 1844-1864. %F A129875 See Quaintance reference for generating functions that produce A129872-A129886. %K A129875 nonn,more %O A129875 1,2 %A A129875 _N. J. A. Sloane_, May 26 2007