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A055969 Number of unlabeled digraphs with n nodes and an odd number of arcs. 2
0, 1, 6, 104, 4736, 770112, 440994608, 896679244544, 6513978322585408, 170630215971902124288, 16261454692523251085611648, 5683372715412699486531047331840, 7334542846356464931239079919515090432, 35157828307617499760690834338506768579289088 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..50

FORMULA

a(n) = (A000273(n)-A003086(n))/2.

MATHEMATICA

A000273 = Cases[Import["https://oeis.org/A000273/b000273.txt", "Table"], {_, _}][[All, 2]];

A003086 = Cases[Import["https://oeis.org/A003086/b003086.txt", "Table"], {_, _}][[All, 2]];

a[n_] := (A000273[[n + 1]] - A003086[[n]])/2;

Array[a, 50] (* Jean-Fran├žois Alcover, Sep 12 2019, after Andrew Howroyd *)

CROSSREFS

Cf. A054928, A007869, A054960.

Sequence in context: A106304 A006676 A006768 * A285027 A184188 A112822

Adjacent sequences:  A055966 A055967 A055968 * A055970 A055971 A055972

KEYWORD

easy,nonn

AUTHOR

Vladeta Jovovic, Jul 19 2000

EXTENSIONS

Terms a(14) and beyond from Andrew Howroyd, Sep 17 2018

STATUS

approved

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Last modified June 23 08:35 EDT 2021. Contains 345395 sequences. (Running on oeis4.)