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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 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.)