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 A018196 #13 Dec 12 2015 02:08:30 %S A018196 1,4,8,9,15,32 %N A018196 Possible numbers of complements of topologies on 5 points. %H A018196 J. I. Brown and S. Watson, <a href="http://dx.doi.org/10.1016/0012-365X(95)00004-G">The number of complements of a topology on n points is at least 2^n (except for some special cases)</a>, Discr. Math., 154 (1996), 27-39. %Y A018196 Cf. A000798. %K A018196 nonn,more,fini %O A018196 0,2 %A A018196 _N. J. A. Sloane_