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 A129881 #5 Mar 30 2013 04:52:00
%S A129881 2,2,6,6,22,24,90,100
%N A129881 Sequence i_{s_n} arising in enumeration of arrays of directed blocks (see Quaintance reference for precise definition), where i_n = A129876, s_n = A129873.
%D A129881 Jocelyn Quaintance, Combinatoric Enumeration of Two-Dimensional Proper Arrays, Discrete Math., 307 (2007), 1844-1864.
%F A129881 See Quaintance reference for generating functions that produce A129872-A129886.
%K A129881 nonn,more
%O A129881 1,1
%A A129881 _N. J. A. Sloane_, May 26 2007