%I #20 Apr 05 2024 11:07:04
%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 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_.