A229638 Number of defective 3-colorings of a 2 X n 0..2 array connected horizontally, diagonally and antidiagonally with exactly two mistakes, and colors introduced in row-major 0..2 order.

0, 6, 40, 122, 488, 1608, 5392, 17368, 55232, 172896, 535296, 1641376, 4992896, 15083648, 45297408, 135323008, 402405376, 1191699968, 3516119040, 10339711488, 30313351168, 88624646144, 258445856768, 751910639616, 2182836600832

Offset: 1

Author

R. H. Hardin, Sep 27 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Row 2 of A229637.

Formula

Empirical: a(n) = 6*a(n-1) - 6*a(n-2) - 16*a(n-3) + 12*a(n-4) + 24*a(n-5) + 8*a(n-6).

Empirical g.f.: 2*x^2*(1 - x)*(3 + 5*x - 36*x^2 + 10*x^3) / (1 - 2*x - 2*x^2)^3. - Colin Barker, Sep 20 2018