cp's OEIS Frontend

A326252 Number of digraphs with vertices {1..n} whose increasing edges are crossing.

%I A326252 #5 Jun 30 2019 06:50:06
%S A326252 0,0,0,0,16384,22020096,62679678976,556181084962816
%N A326252 Number of digraphs with vertices {1..n} whose increasing edges are crossing.
%C A326252 A directed edge (a,b) is increasing if a < b. Two edges (a,b), (c,d) are crossing if a < c < b < d or c < a < d < b.
%F A326252 a(n) = 2^(n * (n + 1)/2) * A326210(n).
%t A326252 croXQ[eds_]:=MatchQ[eds,{___,{x_,y_},___,{z_,t_},___}/;x<z<y<t||z<x<t<y];
%t A326252 Table[Length[Select[Subsets[Tuples[Range[n],2]],croXQ[#]&]],{n,0,4}]
%Y A326252 Simple graphs whose edges are crossing are A326210.
%Y A326252 Digraphs whose increasing edges are not crossing are A326251.
%Y A326252 Digraphs whose edges are not crossing are A326237.
%Y A326252 Cf. A002416, A002720, A229865, A324170, A326209, A326252, A326258.
%K A326252 nonn,more
%O A326252 0,5
%A A326252 _Gus Wiseman_, Jun 30 2019