A229581 Number of defective 3-colorings of an n X 3 0..2 array connected horizontally and antidiagonally with exactly one mistake, and colors introduced in row-major 0..2 order.

2, 28, 264, 2160, 16416, 119232, 839808, 5785344, 39191040, 262020096, 1733363712, 11367641088, 74010599424, 478892113920, 3082323787776, 19747769352192, 126009575866368, 801195213717504, 5077997833420800, 32092946307219456

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 12*a(n-1) - 36*a(n-2).

Conjectures from Colin Barker, Sep 19 2018: (Start)

G.f.: 2*(1 + 2*x) / (1 - 6*x)^2.

a(n) = 2^(n + 1) * 3^(n - 1) * (4*n + 3).

(End)

Example

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

Crossrefs

Column 3 of A229586.

Sequence in context: A326248 A230270 A230759 * A230589 A097353 A092801

Adjacent sequences: A229578 A229579 A229580 * A229582 A229583 A229584

Keyword

nonn

Author

R. H. Hardin, Sep 26 2013

Status

approved