A326225 - OEIS

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A326225

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

11

0, 1, 1, 4, 61, 3725, 844141, 626078904

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

OFFSET

0,4

COMMENTS

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

LINKS

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

Sean A. Irvine, Non-isomorphic representatives of the a(5) = 3725 non-Hamiltonian digraphs (without loops)

Gus Wiseman, Non-isomorphic representatives of the a(4) = 61 non-Hamiltonian digraphs (without loops)

EXAMPLE

Non-isomorphic representatives of the a(3) = 4 digraph edge-sets:

{12,23,31}

{12,13,21,32}

{12,13,21,23,31}

{12,13,21,23,31,32}

CROSSREFS

The labeled case is A326219.

The case with loops is A326226.

The undirected case is A003216.

Non-Hamiltonian unlabeled digraphs (without loops) are A326222.

Cf. A000595, A002416, A003087, A003216, A053763, A246446, A326204, A326218, A326223.

Sequence in context: A262654 A218472 A304176 * A102193 A376736 A232156

Adjacent sequences: A326222 A326223 A326224 * A326226 A326227 A326228

KEYWORD

nonn,hard,more

AUTHOR

Gus Wiseman, Jun 15 2019

EXTENSIONS

a(5)-a(7) from Sean A. Irvine, Jun 16 2019

STATUS

approved