A233726 Number of (n+1) X (1+1) 0..3 arrays with every 2 X 2 subblock having the sum of the absolute values of the edge differences equal to 6 and no adjacent elements equal.

40, 148, 556, 2104, 7976, 30260, 114820, 435720, 1653488, 6274804, 23812172, 90364680, 342924296, 1301361476, 4938528804, 18741194360, 71120848176, 269896091748, 1024227097996, 3886833426776, 14750121431720, 55975149559572

Offset: 1

Author

R. H. Hardin, Dec 15 2013

Keywords

• nonn

Examples

			Some solutions for n=5:
..0..2....3..1....3..2....0..2....2..3....0..1....0..1....1..3....0..2....3..0
..2..1....2..0....2..0....1..3....1..0....1..3....1..3....0..2....1..3....2..1
..0..2....1..2....0..1....0..1....0..2....2..1....0..1....2..1....3..2....3..0
..2..3....0..3....2..3....3..2....2..1....0..2....2..0....1..3....0..1....2..1
..1..0....1..2....3..1....0..1....0..2....2..1....0..1....0..2....2..0....0..2
..3..2....2..0....1..0....1..3....1..0....1..3....1..3....1..3....0..1....2..1
		

Links

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

Crossrefs

Column 1 of A233733.

Formula

Empirical: a(n) = 3*a(n-1) + 5*a(n-2) - 7*a(n-3) - 2*a(n-4).

Empirical g.f.: 4*x*(10 + 7*x - 22*x^2 - 6*x^3) / (1 - 3*x - 5*x^2 + 7*x^3 + 2*x^4). - Colin Barker, Oct 11 2018