%I #4 Mar 30 2012 17:40:41

%S 1,4,16,80,8448,907904,81949952

%N Number of real n X n symmetric (+1,-1) matrices with negative determinant.

%F a(2n+1) = A118994(2n+1) [From _Max Alekseyev_, May 08 2009]

%Y Cf. A118999, A118994.

%K nonn,more

%O 1,2

%A _Giovanni Resta_, May 08 2006