A199649 Number of n X 2 0..2 arrays with values 0..2 introduced in row major order and each element equal to no more than two horizontal and vertical neighbors.

2, 14, 113, 953, 8037, 67774, 571530, 4819638, 40643380, 342740340, 2890284724, 24373395288, 205537673480, 1733272476824, 14616461440144, 123258718919184, 1039424750772560, 8765333779162336, 73916920107029408, 623331776719986016

Offset

1,1

Comments

Column 2 of A199655.

Links

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

Formula

Empirical: a(n) = 8*a(n-1) + 4*a(n-2) - 2*a(n-3) - 8*a(n-4) for n>6.

Empirical g.f.: x*(2 - 2*x - 7*x^2 - 3*x^3 + 5*x^4 + 4*x^5) / (1 - 8*x - 4*x^2 + 2*x^3 + 8*x^4). - Colin Barker, Mar 02 2018

Example

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

Crossrefs

Cf. A199655.

Sequence in context: A214766 A330553 A275649 * A357584 A216581 A192406

Adjacent sequences: A199646 A199647 A199648 * A199650 A199651 A199652

Keyword

nonn

Author

R. H. Hardin, Nov 08 2011

Status

approved