A183323 Number of n X n binary arrays with each 1 adjacent to exactly two other 1s

1, 2, 6, 27, 289, 4740, 128371, 6115158, 505971397, 73890230419, 19136191954838, 8704355999401819, 6908686513461201175, 9552034660752931158279

Offset

1,2

Comments

Diagonal of A183328

Links

Table of n, a(n) for n=1..14.

Example

Some solutions for 6X6
..1..1..1..0..0..0....0..1..1..1..1..0....0..0..0..1..1..1....0..0..1..1..1..1
..1..0..1..0..1..1....0..1..0..0..1..1....0..0..1..1..0..1....0..0..1..0..0..1
..1..0..1..0..1..1....1..1..0..0..0..1....0..1..1..0..1..1....1..1..1..0..0..1
..1..1..1..0..0..0....1..0..0..0..1..1....0..1..0..1..1..0....1..0..0..0..0..1
..0..0..0..1..1..0....1..1..0..1..1..0....0..1..0..1..0..0....1..0..0..0..1..1
..0..0..0..1..1..0....0..1..1..1..0..0....0..1..1..1..0..0....1..1..1..1..1..0

Crossrefs

Sequence in context: A003513 A113731 A113676 * A153253 A174880 A303394

Adjacent sequences: A183320 A183321 A183322 * A183324 A183325 A183326

Keyword

nonn

Author

R. H. Hardin Jan 03 2011

Status

approved