A221257 Number of 3Xn arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no occupancy greater than 2.

0, 16, 30, 2116, 22268, 488601, 7356420, 132273001, 2175160988, 37343243536, 627439570380, 10652755988736, 179923226827008, 3046558564618321, 51520912019433840, 871812703964410321, 14747896839403221578

Offset: 1

Author

R. H. Hardin Jan 06 2013

Keywords

• nonn

Comments

Row 3 of A221255

Examples

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

Links

• R. H. Hardin, Table of n, a(n) for n = 1..36

Formula

Empirical: a(n) = 21*a(n-1) +21*a(n-2) -1891*a(n-3) +4713*a(n-4) +31527*a(n-5) -98973*a(n-6) -92217*a(n-7) +299577*a(n-8) -27117*a(n-9) +103383*a(n-10) -393*a(n-11) +6211*a(n-12) +69*a(n-13) +69*a(n-14) +a(n-15) for n>18