A229601 Number of defective 3-colorings of an n X 3 0..2 array connected horizontally and vertically with exactly two mistakes, and colors introduced in row-major 0..2 order.

1, 39, 396, 3040, 20714, 131345, 792929, 4618048, 26165860, 145058507, 790042315, 4239980962, 22473980838, 117862612005, 612450538677, 3156938117780, 16157454978232, 82173962646319, 415564115855215, 2090880090793526

Offset

1,2

Links

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

Formula

Empirical: a(n) = 15*a(n-1) - 81*a(n-2) + 185*a(n-3) - 162*a(n-4) + 60*a(n-5) - 8*a(n-6) for n>7.

Empirical g.f.: x*(1 + 24*x - 108*x^2 + 74*x^3 + 137*x^4 - 127*x^5 + 8*x^6) / (1 - 5*x + 2*x^2)^3. - Colin Barker, Sep 19 2018

Example

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

Crossrefs

Column 3 of A229606.

Sequence in context: A233369 A238102 A266172 * A210335 A210328 A231993

Adjacent sequences: A229598 A229599 A229600 * A229602 A229603 A229604

Keyword

nonn

Author

R. H. Hardin, Sep 26 2013

Status

approved