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

Author

R. H. Hardin, Sep 26 2013

Keywords

• nonn

Examples

			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
		

Links

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

Crossrefs

Column 3 of A229606.

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