A096368 Number of unlabeled regular tournaments with 2n+1 nodes.

1, 1, 1, 3, 15, 1223, 1495297, 18400989629, 2406183070160597, 3511056114693589781331, 59423289286172717542785192911, 12034362241475984037791303316068785847, 29921426689289629541982244885554389482859734381

Offset

0,4

Comments

Terms may be computed without generating each tournament by enumerating the number of tournaments by degree sequence. A PARI program showing this technique for labeled tournaments is given in A007079. Burnside's lemma as applied in A000568 can be used to extend this method to the unlabeled case. - Andrew Howroyd, Mar 13 2020

Links

Table of n, a(n) for n=0..12.

Gunnar Brinkmann, Generating regular directed graphs, Discrete Math., 313 (2012), 1-7. [N. J. A. Sloane, Nov 26 2012]

Marc Chamberland and Eugene A. Herman, Rock-paper-scissors meets Borromean rings, The Mathematical Intelligencer, 37(2), 20--25.

Marc Chamberland, What's Better than Rock Paper Scissors? (2014).

B. D. McKay, Catalogues of directed graphs.

B. D. McKay, The asymptotic numbers of regular tournaments, Eulerian digraphs and Eulerian oriented graphs, Combinatorica 10 (1990), 367-377.

Crossrefs

Cf. A000568, A007079.

Sequence in context: A012766 A012796 A231656 * A016066 A012848 A322714

Adjacent sequences: A096365 A096366 A096367 * A096369 A096370 A096371

Keyword

more,nonn

Author

David J. Haglin (david.haglin(AT)mnsu.edu), Jul 02 2004

Extensions

Offset and count for 15 vertices corrected by Brendan McKay, Dec 09 2008

a(0) from Álvar Ibeas, Nov 18 2017

a(8)-a(12) from Andrew Howroyd, Mar 13 2020

Status

approved