A118990 Number of symmetric singular n X n (+1,-1) matrices over the reals.

0, 4, 32, 512, 15872, 907008, 104535552, 22523623424, 9599255461888, 7747175087620096

Offset: 1

Author

Giovanni Resta, May 08 2006

Keywords

• nonn
• more

Crossrefs

Cf. A086906, A119010, A057982, A118992.

Formula

a(n) = 2^(n*(n+1)/2) - A118994(n) - A118997(n) = 2^(n*(n+1)/2) - A118992(n). - Max Alekseyev, May 08 2009

Extensions

a(8)-a(10) from Max Alekseyev, Jun 17 2025