A180976 Number of n X n binary matrices with floor(n^2/2) 1's and rows and columns in lexicographically strictly increasing order

1, 1, 5, 50, 1823, 189359, 61746973, 57086318681, 174484293356777, 1558231919489703557

Offset

1,3

Comments

Diagonal of A180977

Links

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

Example

All solutions for 3X3
..0..0..0....0..0..1....0..0..1....0..0..1....0..0..1
..0..1..1....0..1..0....0..1..0....0..1..0....0..1..1
..1..0..1....0..1..1....1..1..0....1..0..1....1..0..0

Crossrefs

Sequence in context: A247951 A082100 A299353 * A305844 A303132 A070995

Adjacent sequences: A180973 A180974 A180975 * A180977 A180978 A180979

Keyword

nonn

Author

R. H. Hardin Sep 30 2010

Status

approved