A221894 Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal, vertical or antidiagonal neighbor, without move-in move-out straight through or left turns.

3, 31, 266, 2305, 19936, 172624, 1494152, 12933821, 111957318, 969123166, 8388906524, 72615905296, 628576515760, 5441072941952, 47098919537873, 407696835820987, 3529098152699791, 30548517126329090, 264433534642030465

Offset: 1

Author

R. H. Hardin, Jan 30 2013

Keywords

• nonn

Comments

Column 2 of A221898.

Examples

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

Links

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

Crossrefs

Cf. A221898.

Formula

Empirical: a(n) = 5*a(n-1) + 26*a(n-2) + 45*a(n-3) + 34*a(n-4) - 2*a(n-5) - 4*a(n-6) + a(n-7).

Empirical g.f.: x*(3 + 16*x + 33*x^2 + 34*x^3 - 2*x^4 - 4*x^5 + x^6) / (1 - 5*x - 26*x^2 - 45*x^3 - 34*x^4 + 2*x^5 + 4*x^6 - x^7). - Colin Barker, Aug 11 2018