A221135 Number of nX4 arrays of occupancy after each element moves to some horizontal or vertical neighbor, with no occupancy greater than 2.

4, 289, 12544, 643204, 31203396, 1539699121, 75512292025, 3709710975721, 182118668668225, 8941989810789025, 439009303948483984, 21553427021714858449, 1058163003670012270144, 51950295646215686851681

Offset: 1

Author

R. H. Hardin Jan 02 2013

Keywords

• nonn

Comments

Column 4 of A221139

Examples

			Some solutions for n=3
..2..2..2..1....2..1..1..1....1..2..2..0....0..1..2..0....2..2..1..0
..1..0..1..1....2..1..0..1....1..0..1..2....2..2..1..0....0..1..1..1
..1..0..0..1....0..2..1..0....1..1..0..1....0..1..2..1....1..2..0..1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..23