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 A054933 Number of unlabeled digraphs on n nodes up to reversing the arcs. 2
 1, 3, 13, 144, 5158, 778084, 441288796, 896699384640, 6513980949408584, 170630216624502796000, 16261454692830032538976880, 5683372715412978313604073582912, 7334542846356465411966209047539403296, 35157828307617499762304829312302735958971072, 629172630775224433640531447950565255471723325434560 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Andrew Howroyd, Table of n, a(n) for n = 1..50 A. Gainer-Dewar, PĆ³lya theory for species with an equivariant group action, arXiv:1401.6202 [math.CO], 2014. Also Andrew Gainer-Dewar, Species with an equivariant group action, AUSTRALASIAN JOURNAL OF COMBINATORICS, Volume 63(2) (2015), Pages 202-225. V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2. FORMULA a(n) = (A000273(n) + A002499(n))/2. CROSSREFS Cf. A000273, A002499. Sequence in context: A228648 A161677 A180276 * A130589 A041591 A001150 Adjacent sequences:  A054930 A054931 A054932 * A054934 A054935 A054936 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, May 24 2000 STATUS approved

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Last modified February 16 20:45 EST 2019. Contains 320189 sequences. (Running on oeis4.)