A221689 Number of n X 3 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without consecutive moves in the same direction.

6, 152, 3112, 63676, 1302720, 26650988, 545221260, 11154026300, 228186749552, 4668196767064, 95500991265668, 1953739262283024, 39969188300499044, 817681276128120100, 16727952148700884996, 342216938625170086928

Offset: 1

Author

R. H. Hardin, Jan 22 2013

Keywords

• nonn

Comments

Column 3 of A221693.

Examples

			Some solutions for n=3:
..0..4..0....0..3..0....0..2..1....0..2..2....0..3..1....1..1..1....1..2..0
..1..0..0....1..1..0....0..1..0....0..1..0....0..1..0....1..1..0....1..2..1
..1..1..2....2..2..0....2..1..2....1..1..2....2..1..1....0..4..0....0..2..0
		

Links

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

Crossrefs

Cf. A221693.

Formula

Empirical: a(n) = 24*a(n-1) - 69*a(n-2) - 71*a(n-3) + 2*a(n-4) for n>5.

Empirical g.f.: 2*x*(3 + 4*x - 61*x^2 - 49*x^3 + 2*x^4) / (1 - 24*x + 69*x^2 + 71*x^3 - 2*x^4). - Colin Barker, Aug 10 2018