A221777 Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal, diagonal or antidiagonal neighbor, without move-in move-out left turns.

3, 25, 184, 1367, 10179, 75782, 564169, 4200043, 31267890, 232778781, 1732958641, 12901286112, 96045675555, 715027301353, 5323134422488, 39628920498935, 295023799000179, 2196351575583206, 16351088488165993, 121728277803994939

Offset

1,1

Comments

Column 2 of A221780.

Links

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

Formula

Empirical: a(n) = 8*a(n-1) - 5*a(n-2) + 7*a(n-3) - 4*a(n-4) - a(n-5).

Empirical g.f.: x*(3 + x - x^2 - x^3) / ((1 + x^2)*(1 - 8*x + 4*x^2 + x^3)). - Colin Barker, Mar 14 2018

Example

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

Crossrefs

Cf. A221780.

Sequence in context: A303602 A000544 A356200 * A227995 A037776 A037664

Adjacent sequences: A221774 A221775 A221776 * A221778 A221779 A221780

Keyword

nonn

Author

R. H. Hardin, Jan 25 2013

Status

approved