A054955 Number of labeled Eulerian digraphs with n nodes and an even number of edges.

1, 2, 8, 88, 3928, 688336, 438953344, 1023160206720, 8829110851362176, 284886609918484446976, 34640035331694391965082624, 15970703846423879100652101753856, 28060860469435555251136195653129640960, 188681219498365676664628141013181402003089408

Offset

1,2

Links

Table of n, a(n) for n=1..14.

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

Formula

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

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 *)

Crossrefs

Cf. A007080, A054956.

Sequence in context: A132316 A136749 A226321 * A012299 A012295 A009486

Adjacent sequences: A054952 A054953 A054954 * A054956 A054957 A054958

Keyword

nonn,easy

Author

N. J. A. Sloane, May 24 2000

Extensions

More terms from Vladeta Jovovic, Mar 05 2001

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

Status

approved