A199641 Number of n X 2 0..2 arrays with values 0..2 introduced in row major order and each element equal to one or two horizontal and vertical neighbors.

1, 3, 13, 60, 288, 1384, 6628, 31772, 152304, 730036, 3499340, 16773680, 80402532, 385399644, 1847365808, 8855120468, 42445929772, 203459338800, 975257291396, 4674775757500, 22407962058928, 107409807372276, 514855687878924

Offset

1,2

Comments

Column 2 of A199647.

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) for n>7.

Empirical g.f.: x*(1 - 3*x^2 - 8*x^3 - 7*x^4 + 4*x^5 + 4*x^6) / (1 - 3*x - 7*x^2 - 8*x^3 + 8*x^5). - Colin Barker, May 16 2018

Example

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

Crossrefs

Cf. A199647.

Sequence in context: A074437 A026578 A362596 * A357151 A367058 A353208

Adjacent sequences: A199638 A199639 A199640 * A199642 A199643 A199644

Keyword

nonn

Author

R. H. Hardin, Nov 08 2011

Status

approved