A326222 Number of non-Hamiltonian unlabeled n-vertex digraphs (without loops).

1, 0, 2, 12, 157, 5883, 696803, 255954536

Offset: 0

Author

Gus Wiseman, Jun 15 2019

Keywords

• nonn
• hard
• more

Comments

A digraph is Hamiltonian if it contains a directed cycle passing through every vertex exactly once.

Links

• Gus Wiseman, Non-isomorphic representatives of the a(3) = 12 non-Hamiltonian digraphs.

Crossrefs

The labeled case is A326218 (without loops) or A326220 (with loops).

The undirected case (without loops) is A246446.

The case with loops is A326223.

Hamiltonian unlabeled digraphs are A326225 (without loops) or A003216 (with loops).

Cf. A000273, A000595, A002416, A003087, A053763, A326216, A326217, A326224, A326226.

Formula

a(n) = A000273(n) - A326225(n). - Pontus von Brömssen, Mar 17 2024

Extensions

a(5)-a(7) (using A000273 and A326225) from Pontus von Brömssen, Mar 17 2024