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 A222320 #5 Apr 10 2013 13:46:16 %S A222320 1,2,4,8,20,52,146,430,1306,4176,13832,47452,169044,619672,234225 %N A222320 Number of open Skolem sequences of order n. %H A222320 S. Burrill and L. Yen, <a href="http://arxiv.org/abs/1301.6424">Constructing Skolem sequences via generating trees</a>, arXiv preprint arXiv:1301.6424, 2013 %Y A222320 Cf. A004075. %K A222320 nonn,more %O A222320 1,2 %A A222320 _N. J. A. Sloane_, Feb 18 2013