A326224 Number of unlabeled n-vertex digraphs (with loops) not containing a Hamiltonian path.

1, 2, 3, 30, 649

Offset

0,2

Comments

A directed path is Hamiltonian if it passes through every vertex exactly once.

Links

Table of n, a(n) for n=0..4.

Wikipedia, Hamiltonian path

Gus Wiseman, Enumeration of paths and cycles and e-coefficients of incomparability graphs, arXiv:0709.0430 [math.CO], 2007.

Gus Wiseman, Non-isomorphic representatives of the a(3) = 30 digraphs not containing a Hamiltonian path.

Formula

A000595(n) = a(n) + A326221(n).

Crossrefs

The labeled case is A326213.

The undirected case is A283420 (without loops).

Unlabeled digraphs containing a Hamiltonian path are A326221.

Unlabeled digraphs not containing a Hamiltonian cycle are A326223.

Cf. A000595, A002416, A003087, A003216, A057864.

Sequence in context: A203431 A137981 A110351 * A270483 A217370 A088115

Adjacent sequences: A326221 A326222 A326223 * A326225 A326226 A326227

Keyword

nonn,more

Author

Gus Wiseman, Jun 16 2019

Status

approved