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A219889
Number of directed 2-regular graphs on n nodes.
12
1, 2, 5, 23, 92, 624, 5021, 47034, 494320, 5719769, 71971687
OFFSET
3,2
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)
Sequence in context: A106858 A376156 A290887 * A369834 A100299 A371308
KEYWORD
nonn,more
AUTHOR
N. J. A. Sloane, Nov 30 2012
STATUS
approved