%I #17 Dec 17 2016 10:28:43
%S 192,21504,190080,573440,218880,40480,2106,53329920
%N Denominator of mass (Sum 1/|Aut(H)|) of Hadamard matrices of order 4n.
%H V. Alvarez, J. A. Armario, M. D. Frau and F. Gudiel, <a href="http://dx.doi.org/10.1016/j.laa.2011.05.018">The maximal determinant of cocyclic (-1, 1)-matrices over D_{2t}</a>, Linear Algebra and its Applications, 2011.
%H <a href="/index/Ha#Hadamard">Index entries for sequences related to Hadamard matrices</a>
%e 1/192, 1/21504, 1/190080, 27/573440, 127/218880, 34603/40480, 278617/2106, 264156210586399/53329920, ...
%Y Cf. A048615, A007299, A036297.
%K frac,nonn,hard,nice
%O 1,1
%A _N. J. A. Sloane_, E. M. Rains
%E a(8) from _Brendan McKay_, Feb 11 2012