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

Author

R. H. Hardin Jan 03 2011

Keywords

• nonn

Comments

Diagonal of A183328

Examples

			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