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A005535 Number of semi-regular digraphs (with loops) on n unlabeled nodes with each node having out-degree 3.
(Formerly M5081)
2
1, 19, 916, 91212, 12888450, 2411213698, 575737451509, 171049953499862, 61944438230597774, 26879022100485977540, 13773587720396658214925, 8231894671550187551622795, 5676740663627528580559535893, 4474748487205893704072253926113 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,2

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Andrew Howroyd, Table of n, a(n) for n = 3..50

S. A. Choudum, K. R. Parthasarathy, Semi-regular relations and digraphs, Nederl. Akad. Wetensch. Proc. Ser. A. {75}=Indag. Math. 34 (1972), 326-334.

CROSSREFS

Column k=3 of A259471.

Cf. A003286, A185193.

Sequence in context: A183473 A217826 A209353 * A171226 A247279 A192569

Adjacent sequences:  A005532 A005533 A005534 * A005536 A005537 A005538

KEYWORD

nonn,nice

AUTHOR

N. J. A. Sloane

EXTENSIONS

a(7) from Sean A. Irvine, Jul 07 2016

Terms a(8) and beyond from Andrew Howroyd, Sep 13 2020

STATUS

approved

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Last modified November 30 15:45 EST 2020. Contains 338807 sequences. (Running on oeis4.)