A183476 Number of n X 2 0..2 arrays with every element equal to either the sum mod 3 of its vertical neighbors or the sum mod 3 of its horizontal neighbors.

3, 15, 39, 135, 495, 1647, 5751, 20223, 70119, 244863, 855927, 2985903, 10426887, 36416223, 127148535, 444006927, 1550518119, 5414352255, 18907098327, 66024403695, 230558764743, 805118884191, 2811503074743, 9817858453455

Offset

1,1

Comments

Column 2 of A183483.

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 12*a(n-3) - 18*a(n-4) - 36*a(n-6).

Empirical g.f.: 3*x*(1 + 2*x - 2*x^2 - 6*x^3 - 12*x^4 - 12*x^5) / ((1 - 6*x^3)*(1 - 3*x - 6*x^3)). - Colin Barker, Mar 29 2018

Example

Some solutions for 4 X 2.
..2..2....2..2....1..1....0..0....2..2....0..0....0..0....2..2....0..0....1..1
..0..0....2..2....0..2....0..0....1..1....1..1....2..0....0..0....2..2....1..1
..1..1....0..0....2..1....1..1....0..0....1..1....2..0....2..2....1..1....2..2
..0..0....1..1....2..2....0..0....2..2....1..1....0..0....2..2....1..1....0..0

Crossrefs

Cf. A183483.

Sequence in context: A065765 A318738 A146853 * A297621 A014309 A298049

Adjacent sequences: A183473 A183474 A183475 * A183477 A183478 A183479

Keyword

nonn

Author

R. H. Hardin, Jan 05 2011

Status

approved