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%I #13 Mar 17 2024 12:53:30
%S 1,0,2,12,157,5883,696803,255954536
%N Number of non-Hamiltonian unlabeled n-vertex digraphs (without loops).
%C A digraph is Hamiltonian if it contains a directed cycle passing through every vertex exactly once.
%H Gus Wiseman, <a href="/A326222/a326222_1.png">Non-isomorphic representatives of the a(3) = 12 non-Hamiltonian digraphs</a>.
%F a(n) = A000273(n) - A326225(n). - _Pontus von Brömssen_, Mar 17 2024
%Y The labeled case is A326218 (without loops) or A326220 (with loops).
%Y The undirected case (without loops) is A246446.
%Y The case with loops is A326223.
%Y Hamiltonian unlabeled digraphs are A326225 (without loops) or A003216 (with loops).
%Y Cf. A000273, A000595, A002416, A003087, A053763, A326216, A326217, A326224, A326226.
%K nonn,hard,more
%O 0,3
%A _Gus Wiseman_, Jun 15 2019
%E a(5)-a(7) (using A000273 and A326225) from _Pontus von Brömssen_, Mar 17 2024
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