A Graph in which each Edge is replaced by a directed Edge, also called a Digraph or Reflexive Graph. A Complete directed graph is called a Tournament. If is an undirected connected Graph, then one can always direct the circuit Edges of and leave the Separating Edges undirected so that there is a directed path from any node to another. Such a Graph is said to be transitive if the adjacency relation is transitive. The number of directed graphs of nodes for , 2, ... are 1, 3, 16, 218, 9608, ... (Sloane's A000273).
See also Arborescence, Cayley Graph, Indegree, Network, Outdegree, Sink (Directed Graph), Source, Tournament
Sloane, N. J. A. Sequence
in ``An On-Line Version of the Encyclopedia of Integer Sequences.''
http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S.
The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.