A055969 Number of unlabeled digraphs with n nodes and an odd number of arcs.

0, 1, 6, 104, 4736, 770112, 440994608, 896679244544, 6513978322585408, 170630215971902124288, 16261454692523251085611648, 5683372715412699486531047331840, 7334542846356464931239079919515090432, 35157828307617499760690834338506768579289088

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-François Alcover, Sep 12 2019, after Andrew Howroyd *)

Crossrefs

Cf. A054928, A007869, A054960.

Sequence in context: A106304 A006676 A006768 * A285027 A184188 A356008

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