A003088 Number of unilateral digraphs with n unlabeled nodes.

1, 1, 2, 11, 171, 8603, 1478644, 870014637

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• nice
• more

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

Cf. A057270, A003029 (labeled case), A003085, A035512, A051421, A049531, A049512.

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