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

1,2

Links

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

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

Example

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

Crossrefs

Row 2 of A229637.

Sequence in context: A211065 A002595 A263956 * A210291 A336317 A089207

Adjacent sequences: A229635 A229636 A229637 * A229639 A229640 A229641

Keyword

nonn

Author

R. H. Hardin, Sep 27 2013

Status

approved