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A262327 Number of (n+1) X (3+1) 0..1 arrays with each row and column divisible by 3, read as a binary number with top and left being the most significant bits. 1
6, 15, 90, 351, 2106, 10935, 65610, 378351, 2270106, 13482855, 80897130, 484142751, 2904856506, 17417978775, 104507872650, 626946793551, 3761680761306, 22569180586695, 135415083520170, 812482365290751, 4874894191744506 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 6*a(n-1) + 9*a(n-2) - 54*a(n-3).

Conjectures from Colin Barker, Dec 31 2018: (Start)

G.f.: 3*x*(2 - 7*x - 18*x^2) / ((1 - 3*x)*(1 + 3*x)*(1 - 6*x)).

a(n) = 3^(n-2)*(14 + 2^(2+n)) / 2 for n even.

a(n) = 3^(n-2)*(28 + 2^(2+n)) / 2 for n odd.

(End)

EXAMPLE

Some solutions for n=4:

..0..0..0..0....0..1..1..0....1..0..0..1....0..0..1..1....1..1..1..1

..0..0..0..0....0..1..1..0....1..1..1..1....0..0..1..1....0..0..0..0

..0..0..0..0....0..0..0..0....0..1..1..0....1..0..0..1....1..1..0..0

..1..0..0..1....1..0..0..1....1..0..0..1....1..1..1..1....0..0..1..1

..1..0..0..1....1..0..0..1....1..0..0..1....0..1..1..0....1..1..0..0

CROSSREFS

Column 3 of A262332.

Sequence in context: A013229 A013225 A138547 * A264413 A194265 A129521

Adjacent sequences:  A262324 A262325 A262326 * A262328 A262329 A262330

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 18 2015

STATUS

approved

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Last modified August 9 07:08 EDT 2022. Contains 356018 sequences. (Running on oeis4.)