A086906 Number of symmetric singular n X n (0,1) matrices over the reals.

1, 4, 32, 496, 14172, 816684, 87982904

Offset

1,2

Comments

W. Edwin Clark computed the first entries.

Links

Table of n, a(n) for n=1..7.

Formula

a(n) = 2^(n*(n+1)/2) - A086899(n).

Crossrefs

Cf. A046747, A086899, A086879, A118989.

Sequence in context: A037964 A089285 A209197 * A034663 A192501 A192487

Adjacent sequences: A086903 A086904 A086905 * A086907 A086908 A086909

Keyword

nonn

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 19 2003

Extensions

a(6) and a(7) from Giovanni Resta, May 08 2006

Status

approved