OFFSET
0,3
REFERENCES
F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 218.
Ronald C. Read, email to N. J. A. Sloane, 28 August, 2000.
R. C. Read and R. J. Wilson, An Atlas of Graphs, Oxford, 1998.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
R. W. Robinson, Counting strong digraphs (research announcement), J. Graph Theory 1, 1977, pp. 189-190.
CROSSREFS
KEYWORD
nonn,nice,more
AUTHOR
EXTENSIONS
Note that Read and Wilson incorrectly give a(4) as 172 - thanks to Vladeta Jovovic, Goran Kilibarda for finding this error and for verifying a(5).
a(7) from Sean A. Irvine, Jan 26 2015
STATUS
approved