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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.)