A221089 Number of 3 X n arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor.

0, 16, 270, 6889, 154440, 3538161, 80655102, 1840667409, 41995876248, 958215843225, 21863225325726, 498845926549881, 11381993364572136, 259699010088371841, 5925462372979055550, 135199223931709452321

Offset

1,2

Comments

Row 3 of A221087.

Links

R. H. Hardin, Table of n, a(n) for n = 1..34

Formula

Empirical: a(n) = 24*a(n-1) - 648*a(n-3) + 729*a(n-4) for n>7.

Empirical g.f.: x^2*(16 - 114*x + 409*x^2 - 528*x^3 - 5103*x^4 + 6480*x^5) / ((1 - 24*x + 27*x^2)*(1 - 27*x^2)). - Colin Barker, Aug 03 2018

Example

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

Crossrefs

Cf. A221087.

Sequence in context: A218062 A220757 A166908 * A119290 A161595 A144660

Adjacent sequences: A221086 A221087 A221088 * A221090 A221091 A221092

Keyword

nonn

Author

R. H. Hardin, Jan 01 2013

Status

approved