A221883 Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal, vertical or antidiagonal neighbor, without consecutive moves in the same direction.

3, 33, 326, 3223, 31832, 314426, 3105733, 30676867, 303010527, 2992984402, 29563182686, 292010132356, 2884328060800, 28489930453209, 281409090823688, 2779616346494657, 27455641219994600, 271192906082774221

Offset

1,1

Comments

Column 2 of A221886.

Links

R. H. Hardin, Table of n, a(n) for n = 1..55

Formula

Empirical: a(n) = 7*a(n-1) + 27*a(n-2) + 16*a(n-3) - 18*a(n-4) - 13*a(n-5) + 5*a(n-6) + 3*a(n-7) - a(n-8).

Empirical g.f.: x*(3 + 12*x + 14*x^2 + 2*x^3 - 5*x^4 - 2*x^5 + x^6) / (1 - 7*x - 27*x^2 - 16*x^3 + 18*x^4 + 13*x^5 - 5*x^6 - 3*x^7 + x^8). - Colin Barker, Aug 11 2018

Example

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

Crossrefs

Cf. A221886.

Sequence in context: A097486 A121515 A362478 * A002277 A332087 A001507

Adjacent sequences: A221880 A221881 A221882 * A221884 A221885 A221886

Keyword

nonn

Author

R. H. Hardin, Jan 30 2013

Status

approved