A054956 Number of labeled Eulerian digraphs with n nodes and an odd number of edges.

0, 0, 2, 64, 3808, 687616, 438948304, 1023160166400, 8829110850999296, 284886609918480818176, 34640035331694391925165824, 15970703846423879100651622752256, 28060860469435555251136195646902620160, 188681219498365676664628141013181314824798208

Offset: 1

Author

N. J. A. Sloane, May 24 2000

Keywords

• nonn
• easy

Links

• V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.

Crossrefs

Cf. A007080, A054955.

Programs

Mathematica

A007080 = Cases[Import["https://oeis.org/A007080/b007080.txt", "Table"], {, }][[All, 2]];
a[n_] := (A007080[[n]] - n!)/2;
Array[a, 14] (* Jean-François Alcover, Aug 27 2019 *)

Formula

a(n) = (A007080(n) - n!)/2. - Andrew Howroyd, Sep 10 2018

Extensions

More terms from Vladeta Jovovic, Mar 05 2001

a(12)-a(14) from Andrew Howroyd, Sep 10 2018