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%I #11 Dec 06 2020 17:18:04
%S 0,0,2,9,82,1607,95647,18545153
%N Number of symmetric unlabeled digraphs (unlabeled digraphs with nontrivial automorphism group).
%F a(n) = A000273(n) - A051504(n).
%e For n=4 nodes from the 218 (=A000273(4)) unlabeled nonisomorphic digraphs 136 (=A051504(4)) are asymmetric, so 218 - 136 = 82 are somehow symmetric.
%Y Cf. A000273, A051504.
%K nonn,more
%O 0,3
%A _Labos Elemer_, Jan 11 2002
%E a(7) added using nauty by _Andrew Howroyd_, Dec 06 2020
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