A067309 - OEIS

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A067309

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

1

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

LINKS

Table of n, a(n) for n=0..7.

FORMULA

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

EXAMPLE

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.

Sequence in context: A110567 A123570 A006040 * A087798 A113146 A323769

Adjacent sequences: A067306 A067307 A067308 * A067310 A067311 A067312

KEYWORD

nonn,more

AUTHOR

Labos Elemer, Jan 11 2002

EXTENSIONS

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

STATUS

approved