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%I #15 May 02 2017 21:48:41
%S 1,1,2,2,37,722
%N Number of doubly-regular tournaments of order 4n-1.
%C Equally, number of skew digraphs in switching classes of Hadamard matrices of order 4n.
%H J. Gebel, <a href="/A001014/a001014.txt">Integer points on Mordell curves</a> [Cached copy, after the original web site tnt.math.se.tmu.ac.jp was shut down in 2017]
%H Edward Spence, <a href="http://dx.doi.org/10.1016/0012-365X(93)E0169-5">Classification of Hadamard matrices of order 24 and 28</a>, Discrete Math. 140 (1995), no. 1-3, 185-243.
%K nonn,hard,more,nice
%O 2,3
%A _N. J. A. Sloane_
%E Better name suggested by _Brendan McKay_, Oct 31 2007