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

1,2

Links

Table of n, a(n) for n=1..10.

Formula

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

Crossrefs

Cf. A086906, A119010, A057982, A118992.

Sequence in context: A144935 A153511 A140179 * A127945 A036442 A186339

Adjacent sequences: A118987 A118988 A118989 * A118991 A118992 A118993

Keyword

nonn,more

Author

Giovanni Resta, May 08 2006

Extensions

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

Status

approved