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 A129874 #5 Mar 30 2013 04:53:56 %S A129874 2,1,4,4,16,19,76,98 %N A129874 Sequence h_n arising in enumeration of arrays of directed blocks (see Quaintance reference for precise definition). %D A129874 Jocelyn Quaintance, Combinatoric Enumeration of Two-Dimensional Proper Arrays, Discrete Math., 307 (2007), 1844-1864. %F A129874 See Quaintance reference for generating functions that produce A129872-A129886. %K A129874 nonn,more %O A129874 1,1 %A A129874 _N. J. A. Sloane_, May 26 2007