A206694 Number of n X 2 0..2 arrays avoiding the pattern z-2 z-1 z in any row or column.

9, 81, 676, 5625, 46656, 386884, 3207681, 26594649, 220492801, 1828075536, 15156318321, 125658906256, 1041820324416, 8637585806529, 71613009227809, 593733388556025, 4922560027477764, 40812252925262329, 338368649551172496

Offset: 1

Author

R. H. Hardin, Feb 11 2012

Keywords

• nonn

Comments

Column 2 of A206700.

Examples

			Some solutions for n=4:
..0..1....0..2....0..2....2..0....0..2....2..1....0..1....1..1....1..2....1..2
..2..1....2..2....1..1....0..2....0..2....0..2....2..1....1..0....2..2....2..0
..2..2....0..0....0..0....1..0....2..2....1..2....2..0....1..2....1..2....0..1
..0..0....2..1....0..1....1..2....0..2....0..1....0..1....1..2....2..2....1..0
		

Links

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

Crossrefs

Cf. A206700.

Formula

Empirical: a(n) = 9*a(n-1) -3*a(n-2) -25*a(n-3) +9*a(n-4) +3*a(n-5) -a(n-6).

Empirical g.f.: x*(9 - 26*x^2 + 9*x^3 + 3*x^4 - x^5) / ((1 - 9*x + 6*x^2 - x^3)*(1 - 3*x^2 - x^3)). - Colin Barker, Feb 23 2018