A185552 1/3 the number of n X 2 0..2 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors.

1, 5, 26, 120, 576, 2768, 13256, 63544, 304608, 1460072, 6998680, 33547360, 160805064, 770799288, 3694731616, 17710240936, 84891859544, 406918677600, 1950514582792, 9349551515000, 44815924117856, 214819614744552

Offset

1,2

Comments

Column 2 of A185559.

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

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

Empirical g.f.: x*(1 - x)*(1 + 3*x + 7*x^2 + 6*x^3) / (1 - 3*x - 7*x^2 - 8*x^3 + 8*x^5). - Colin Barker, Apr 16 2018

Example

Some solutions for 4 X 2 with a(1,1)=0!
..0..0....0..2....0..2....0..0....0..0....0..0....0..0....0..0....0..0....0..0
..2..2....0..2....0..2....0..0....0..1....2..1....2..2....0..1....0..2....1..1
..1..1....0..2....1..2....2..2....1..1....2..1....1..0....1..1....0..2....2..2
..2..2....1..1....1..2....2..2....2..2....0..0....1..0....0..0....0..2....0..0

Crossrefs

Cf. A185559.

Sequence in context: A293799 A211606 A005499 * A171702 A254825 A272123

Adjacent sequences: A185549 A185550 A185551 * A185553 A185554 A185555

Keyword

nonn

Author

R. H. Hardin, Jan 31 2011

Status

approved