A203536 Number of nX2 0..2 arrays with every element neighboring horizontally or vertically both a 0 and a 1.

0, 4, 4, 16, 64, 196, 676, 2304, 7744, 26244, 88804, 300304, 1016064, 3437316, 11628100, 39337984, 133079296, 450203524, 1523028676, 5152368400, 17430336576, 58966408900, 199481929956, 674842534144, 2282975946304, 7723252297476

Offset: 1

Author

R. H. Hardin Jan 02 2012

Keywords

• nonn

Comments

Column 2 of A203542

(A135491(n-2))^2 for n>=3

Examples

			Some solutions for n=5
..0..1....1..1....0..0....1..0....0..0....0..1....0..0....0..1....1..0....1..1
..0..1....0..0....1..1....1..0....1..1....0..1....1..1....0..1....1..0....0..0
..2..1....1..2....1..2....0..2....2..0....1..2....2..2....0..1....0..0....2..1
..0..0....1..0....0..0....0..1....1..0....1..0....0..0....0..0....0..1....0..1
..1..1....1..0....1..1....0..1....1..0....1..0....1..1....1..1....0..1....0..1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 2*a(n-1) +3*a(n-2) +6*a(n-3) -a(n-4) -a(n-6)