A strongly connected digraph, also called a strong digraph, is a directed graph in which it is possible to reach any node starting from any other node
by traversing edges in the direction(s) in which they point (Harary and Palmer 1973b,
pp. 260-261). The vertices in a strongly connected
digraph with at least two vertices therefore must
all have indegree of at least 1. The numbers of nonisomorphic
strongly connected simple directed graphs
on ,
2, ... nodes are 1, 1, 5, 83, 5048, 1047008, ... (OEIS A035512).
Harary, F. and Palmer, E. M. Graphical Enumeration. New York: Academic Press, p. 218, 1973a.Harary,
F. and Palmer, E. M. "A Survey of Graphical Enumeration Problems."
In A Survey of Combinatorial Theory (Ed. J. N. Srivastava). Amsterdam,
Netherlands: North-Holland, pp. 259-275, 1973b.Liskovec, V. A.
"A Contribution to the Enumeration of Strongly Connected Digraphs." Dokl.
AN BSSR17, 1077-1080, 1973.Read, R. C. and Wilson,
R. J. An
Atlas of Graphs. Oxford, England: Oxford University Press, 1998.Skiena,
S. "Strong and Weak Connectivity." §5.1.2 in Implementing
Discrete Mathematics: Combinatorics and Graph Theory with Mathematica. Reading,
MA: Addison-Wesley, pp. 94 and 172-174, 1990.Sloane, N. J. A.
Sequence A035512 in "The On-Line Encyclopedia
of Integer Sequences."
,
2, ... nodes are 1, 1, 5, 83, 5048, 1047008, ... (OEIS A035512).
