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A229680 Number of defective 3-colorings of an n X 3 0..2 array connected diagonally and antidiagonally with exactly two mistakes, and colors introduced in row-major 0..2 order. 1
0, 36, 888, 10896, 108000, 959040, 7952256, 62892288, 480370176, 3571983360, 26000455680, 185993957376, 1311390425088, 9133778681856, 62952545157120, 429958047006720, 2913266164432896, 19601071637004288, 131057481860775936 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 3 of A229685.

LINKS

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

FORMULA

Empirical: a(n) = 18*a(n-1) -108*a(n-2) +216*a(n-3) for n>4.

Empirical: G.f. 12*x^2*(10*x+1)*(10*x-3) / (6*x-1)^3. - R. J. Mathar, Sep 29 2013

Empirical a(n) = 2^n*3^(n-3)*(-45 + 4*n + 16*n^2) for n>1. - Colin Barker, Jun 16 2017

EXAMPLE

Some solutions for n=3

..0..0..0....0..0..0....0..0..1....0..0..1....0..0..0....0..1..2....0..1..1

..1..2..2....1..1..2....0..1..2....2..2..0....0..1..1....2..2..0....2..2..2

..0..2..2....1..1..2....0..1..0....2..1..0....0..2..1....1..2..0....1..2..0

CROSSREFS

Sequence in context: A145150 A166790 A001812 * A169836 A335220 A248108

Adjacent sequences:  A229677 A229678 A229679 * A229681 A229682 A229683

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 27 2013

STATUS

approved

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Last modified August 6 18:25 EDT 2020. Contains 336256 sequences. (Running on oeis4.)