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%I #28 Mar 13 2020 20:54:31
%S 1,1,1,3,15,1223,1495297,18400989629,2406183070160597,
%T 3511056114693589781331,59423289286172717542785192911,
%U 12034362241475984037791303316068785847,29921426689289629541982244885554389482859734381
%N Number of unlabeled regular tournaments with 2n+1 nodes.
%C 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
%H Gunnar Brinkmann, <a href="https://doi.org/10.1016/j.disc.2012.09.014">Generating regular directed graphs</a>, Discrete Math., 313 (2012), 1-7. [_N. J. A. Sloane_, Nov 26 2012]
%H Marc Chamberland and Eugene A. Herman, <a href="http://www.math.grinnell.edu/~chamberl/papers/rps.pdf">Rock-paper-scissors meets Borromean rings</a>, The Mathematical Intelligencer, 37(2), 20--25.
%H Marc Chamberland, <a href="https://www.youtube.com/watch?v=aNp_FvYpbZw">What's Better than Rock Paper Scissors?</a> (2014).
%H B. D. McKay, <a href="http://users.cecs.anu.edu.au/~bdm/data/digraphs.html">Catalogues of directed graphs</a>.
%H B. D. McKay, <a href="http://users.cecs.anu.edu.au/~bdm/papers/rt.pdf">The asymptotic numbers of regular tournaments, Eulerian digraphs and Eulerian oriented graphs</a>, Combinatorica 10 (1990), 367-377.
%Y Cf. A000568, A007079.
%K more,nonn
%O 0,4
%A David J. Haglin (david.haglin(AT)mnsu.edu), Jul 02 2004
%E Offset and count for 15 vertices corrected by _Brendan McKay_, Dec 09 2008
%E a(0) from _Álvar Ibeas_, Nov 18 2017
%E a(8)-a(12) from _Andrew Howroyd_, Mar 13 2020
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