A221126 Number of 2 X n arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor.

1, 21, 200, 1950, 19005, 185164, 1803949, 17574675, 171218008, 1668058947, 16250746331, 158319795778, 1542400400537, 15026541578483, 146393213915408, 1426207951308175, 13894558811577567, 135365087812821450

Offset: 1

Author

R. H. Hardin, Jan 02 2013

Keywords

• nonn

Comments

Row 2 of A221125.

Examples

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

Links

• R. H. Hardin, Table of n, a(n) for n = 1..88

Crossrefs

Cf. A221125.

Formula

Empirical: a(n) = 11*a(n-1) - 11*a(n-2) - 12*a(n-3) - 2*a(n-4) for n>6.

Empirical g.f.: x*(1 + 10*x - 20*x^2 - 7*x^3 + 9*x^4 + x^5) / (1 - 11*x + 11*x^2 + 12*x^3 + 2*x^4). - Colin Barker, Aug 04 2018