A221727 Number of nX4 arrays of occupancy after each element stays put or moves to some horizontal, diagonal or antidiagonal neighbor, with every occupancy equal to zero or two.

4, 52, 540, 6188, 71310, 824144, 9525048, 110070012, 1271809066, 14694217628, 169767833676, 1961352594276, 22659537510670, 261784302805272, 3024367348612856, 34940131867655732, 403658398327592910

Offset: 1

Author

R. H. Hardin Jan 22 2013

Keywords

• nonn

Comments

Column 4 of A221728

Examples

			Some solutions for n=3
..0..2..2..0....2..0..0..2....0..0..2..2....2..2..0..0....0..2..0..2
..0..0..0..2....2..2..2..2....0..2..2..2....2..2..2..0....0..2..2..0
..2..2..2..0....0..0..0..0....2..0..0..0....0..0..2..0....2..0..0..2
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..29