%I #2 Mar 30 2012 17:40:41
%S 2,4,32,512,16896,1190144,163899904
%N Number of real n X n invertible symmetric (+1,-1) matrices.
%Y Cf. A056990, A086899, A056989.A118990.
%K nonn,more
%O 1,1
%A _Giovanni Resta_, May 08 2006
