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Number of skew-symmetric Hadamard matrices of order 4n.
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%I #24 Oct 27 2024 12:12:43

%S 1,1,2,2,16,54

%N Number of skew-symmetric Hadamard matrices of order 4n.

%H F. J. Aragon Artacho, J. M. Borwein, M. K. Tam, <a href="https://carmamaths.org/resources/jon/DR_MatrixCompletion.pdf">Douglas-Rachford Feasibility Methods for Matrix Completion Problems</a>, March 2014.

%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 Joseph W. Iverson, John Jasper, and Dustin G. Mixon, <a href="https://arxiv.org/abs/2410.17379">More on the optimal arrangement of 2d lines in C^d</a>, arXiv:2410.17379 [math.MG], 2024. See p. 21.

%H C. Koukouvinos and S. Stylianou, <a href="https://doi.org/10.1016/j.disc.2006.06.037">On skew-Hadamard matrices</a>, Discrete Math., 308 (2008), 2723-2731.

%H Edward Spence, <a href="https://doi.org/10.1016/j.disc.2006.06.037">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_.