A198717 Number of n X 2 0..6 arrays with values 0..6 introduced in row major order and no element equal to any horizontal or vertical neighbor.

1, 4, 34, 499, 10507, 272410, 7817980, 234638905, 7176366133, 221220625936, 6841771033846, 211886983790431, 6565800345745279, 203504808219690982, 6308194354577750032, 195548116214389189477, 6061914804816147034345

Offset: 1

Author

R. H. Hardin, Oct 29 2011

Keywords

• nonn

Comments

Column 2 of A198723.

Examples

			Some solutions with all values 0 to 6 for n=4:
..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..2..3....2..3....2..3....2..3....2..3....2..3....2..0....2..3....2..3....2..3
..4..5....4..5....4..5....4..5....4..1....4..5....3..4....4..5....4..0....1..4
..6..1....6..0....2..6....6..2....5..6....6..4....5..6....0..6....5..6....5..6
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A198723.

Formula

Empirical: a(n) = 55*a(n-1) - 918*a(n-2) + 5818*a(n-3) - 13417*a(n-4) + 8463*a(n-5).

Conjectures from Colin Barker, Feb 22 2018: (Start)

G.f.: x*(1 - 51*x + 732*x^2 - 3517*x^3 + 4419*x^4) / ((1 - x)*(1 - 3*x)*(1 - 7*x)*(1 - 13*x)*(1 - 31*x)).

a(n) = 11/30 + 3^n/8 + 7^(n-1)/6 + 13^(n-1)/12 + 31^(n-1)/120.

(End)