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 A005328 M3118 #19 Sep 04 2017 00:22:48
%S A005328 1,3,28,510,18631,1351413,194192398,55272612720,31184369778961,
%T A005328 34909296450535023,77616063417393956368,343049603717222441078130,
%U A005328 3016429354620114423122804491,52801416275268069417410827891833
%N A005328 Certain subgraphs of a directed graph.
%D A005328 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A005328 E. Andresen, K. Kjeldsen, <a href="http://dx.doi.org/10.1016/0012-365X(76)90054-6">On certain subgraphs of a complete transitively directed graph</a>, Discrete Math. 14 (1976), no. 2, 103-119.
%F A005328 a(n) = p(n-1)*Sum_{j=0..n-2} (-1)^j*(n-1-j)/p(j), where p(0)=1, p(k) = Product_{i=1..k} (2^i - 1) for k > 0. - _Emeric Deutsch_, Jan 23 2005
%p A005328 p:=proc(n) if n=0 then 1 else product(2^i-1,i=1..n) fi end: a:=n->p(n-1)*sum((-1)^j*(n-1-j)/p(j),j=0..n-2): seq(a(n),n=2..17); # _Emeric Deutsch_, Jan 23 2005
%K A005328 nonn
%O A005328 2,2
%A A005328 _N. J. A. Sloane_
%E A005328 More terms from _Emeric Deutsch_, Jan 23 2005