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A229681 Number of defective 3-colorings of an n X 4 0..2 array connected diagonally and antidiagonally with exactly two mistakes, and colors introduced in row-major 0..2 order. 1
0, 360, 10896, 186576, 2700432, 35485776, 437924880, 5169543120, 59031049104, 656886585168, 7159989801744, 76729919248080, 810700618461840, 8463178886657616, 87441690785378832, 895373932606109136 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 4 of A229685.

LINKS

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

FORMULA

Empirical: a(n) = 27*a(n-1) -243*a(n-2) +729*a(n-3) for n>6.

Conjectures from Colin Barker, Jun 16 2017: (Start)

G.f.: 24*x^2*(15 + 49*x - 839*x^2 + 2007*x^3 - 1296*x^4) / (1 - 9*x)^3.

a(n) = 16*3^(2*n-7)*(-449 + 60*n + 256*n^2) for n>3.

(End)

EXAMPLE

Some solutions for n=3

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

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

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

CROSSREFS

Sequence in context: A056322 A056313 A192829 * A054648 A230684 A299955

Adjacent sequences:  A229678 A229679 A229680 * A229682 A229683 A229684

KEYWORD

nonn

AUTHOR

R. H. Hardin Sep 27 2013

STATUS

approved

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Last modified August 15 16:02 EDT 2020. Contains 336505 sequences. (Running on oeis4.)