A067309 Number of symmetric unlabeled digraphs (unlabeled digraphs with nontrivial automorphism group).

0, 0, 2, 9, 82, 1607, 95647, 18545153

Offset: 0

Author

Labos Elemer, Jan 11 2002

Keywords

• nonn
• more

Examples

			For n=4 nodes from the 218 (=A000273(4)) unlabeled nonisomorphic digraphs 136 (=A051504(4)) are asymmetric, so 218 - 136 = 82 are somehow symmetric.
		

Crossrefs

Cf. A000273, A051504.

Formula

a(n) = A000273(n) - A051504(n).

Extensions

a(7) added using nauty by Andrew Howroyd, Dec 06 2020