A221201 Number of 2 X n arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor, with no occupancy greater than 2.

0, 9, 10, 196, 720, 6400, 34272, 242064, 1460368, 9610000, 60194160, 387459856, 2455717680, 15698085264, 99863349040, 636989149456, 4056917039280, 25859869267600, 164758872493872, 1049992515273744, 6690497356781488

Offset: 1

Author

R. H. Hardin, Jan 04 2013

Keywords

• nonn

Comments

Row 2 of A221200.

Examples

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

Links

• R. H. Hardin, Table of n, a(n) for n = 1..86

Crossrefs

Cf. A221200.

Formula

Empirical: a(n) = 7*a(n-1) + 14*a(n-2) - 126*a(n-3) + 504*a(n-5) - 224*a(n-6) - 448*a(n-7) + 256*a(n-8).

Empirical g.f.: x^2*(9 - 53*x + 342*x^3 - 124*x^4 - 448*x^5 + 256*x^6) / ((1 - 2*x)*(1 + 2*x)*(1 - 7*x + 4*x^2)*(1 - 14*x^2 + 16*x^4)). - Colin Barker, Aug 04 2018