A186160 1/4 the number of n X n 0..3 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors.

0, 7, 702, 751266, 5033988714, 268995986029278

Offset: 1

Author

R. H. Hardin Feb 13 2011

Keywords

• nonn

Comments

Diagonal of A186168

Examples

			Some solutions for 4X4 with a(1,1)=0
..0..2..0..2....0..0..2..0....0..2..1..1....0..0..2..2....0..2..2..1
..0..2..0..2....0..0..2..0....0..2..0..0....0..2..1..2....0..0..0..1
..1..2..3..3....2..3..3..3....2..1..1..0....2..2..1..0....2..3..3..1
..1..1..1..1....2..3..2..2....2..2..1..0....3..3..3..0....2..3..0..0