A219889 Number of directed 2-regular graphs on n nodes.

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

Offset: 3

Author

N. J. A. Sloane, Nov 30 2012

Keywords

• nonn
• more

Links

• 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)