A180982 Number of n X n binary matrices with floor(n^2/2) 1's and rows in lexicographically nondecreasing order and columns in strictly increasing order

1, 2, 6, 71, 2403, 238535, 73506103, 64732546521, 189964969385932, 1647943050926969975

Offset

1,2

Comments

Diagonal of A180983

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..0..1
..0..1..1....0..1..0....0..0..1....0..1..0....0..1..0....0..1..1
..1..0..1....0..1..1....0..1..1....1..1..0....1..0..1....1..0..0

Crossrefs

Sequence in context: A000896 A103527 A239543 * A195690 A359365 A329965

Adjacent sequences: A180979 A180980 A180981 * A180983 A180984 A180985

Keyword

nonn

Author

R. H. Hardin Sep 30 2010

Status

approved