A221732 Number of n X 3 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without move-in move-out left turns.

8, 152, 2904, 54888, 1038128, 19634240, 371344456, 7023277960, 132832016296, 2512266303304, 47514764548512, 898651885401840, 16996300388100616, 321452869097777272, 6079672910672787704, 114985511887049164712

Offset

1,1

Comments

Column 3 of A221736.

Links

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

Formula

Empirical: a(n) = 18*a(n-1) + 17*a(n-2) + 6*a(n-3) - 17*a(n-4).

Empirical g.f.: 8*x*(1 + x + 4*x^2 - 2*x^3) / (1 - 18*x - 17*x^2 - 6*x^3 + 17*x^4). - Colin Barker, Aug 10 2018

Example

Some solutions for n=3:
..2..0..0....2..1..0....1..1..1....0..4..0....0..1..2....2..0..1....1..0..0
..0..5..0....0..2..0....0..4..0....0..1..1....1..0..2....0..2..0....2..3..1
..0..2..0....2..1..1....0..0..2....0..1..2....0..2..1....1..2..1....1..0..1

Crossrefs

Cf. A221736.

Sequence in context: A003491 A053606 A367701 * A249931 A123770 A003400

Adjacent sequences: A221729 A221730 A221731 * A221733 A221734 A221735

Keyword

nonn

Author

R. H. Hardin, Jan 22 2013

Status

approved