A219889 - OEIS

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A219889

Number of directed 2-regular graphs on n nodes.

1, 2, 5, 23, 92, 624, 5021, 47034, 494320, 5719769, 71971687

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

OFFSET

3,2

LINKS

Table of n, a(n) for n=3..13.

Gunnar Brinkmann, Generating regular directed graphs, Discrete Math., 313 (2012), 1-7.

R. J. Mathar, OEIS A219889

Richard J. Mathar, 2-regular Digraphs of the Lovelock Lagrangian, arXiv:1903.12477 [math.GM], 2019.

CROSSREFS

Column k=2 of A350910.

Cf. A096368, A219890, A219891, A219892, A219893, A307155 (connected, inverse Euler Trans.), A007107 (labeled), A306827 (multiedges, connected), A002865 (directed 1-regular unlabeled no loops), A005641 (loops allowed)

Sequence in context: A106858 A376156 A290887 * A369834 A100299 A371308

Adjacent sequences: A219886 A219887 A219888 * A219890 A219891 A219892

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane, Nov 30 2012

STATUS

approved