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A184688 1/3 the number of n X 3 0..2 arrays with no element equal both to the element above and to the element to its left. 1
9, 192, 4080, 86688, 1841856, 39133824, 831474432, 17666296320, 375354928128, 7975147677696, 169447570059264, 3600244178460672, 76494210805186560, 1625268730858733568, 34532004706009153536, 733699803838461640704 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 of A184694.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 22*a(n-1) - 16*a(n-2).

Conjectures from Colin Barker, Apr 14 2018: (Start)

G.f.: 3*x*(3 - 2*x) / (1 - 22*x + 16*x^2).

a(n) = ((105-13*sqrt(105))*(11-sqrt(105))^n + (11+sqrt(105))^n*(105+13*sqrt(105))) / 560.

(End)

EXAMPLE

Some solutions for 5 X 3 with a(1,1)=0:

..0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0

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

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

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

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

CROSSREFS

Cf. A184694.

Sequence in context: A307387 A332119 A261826 * A189178 A297517 A116877

Adjacent sequences:  A184685 A184686 A184687 * A184689 A184690 A184691

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 20 2011

STATUS

approved

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Last modified August 10 11:57 EDT 2022. Contains 356039 sequences. (Running on oeis4.)