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A269188 Number of n X 2 0..3 arrays with some element plus some horizontally, diagonally, antidiagonally or vertically adjacent neighbor totalling three no more than once. 1
16, 108, 708, 4476, 27684, 168252, 1008804, 5983164, 35170980, 205214268, 1189853604, 6861684156, 39384946596, 225136169532, 1282284719268, 7279841963964, 41210177357988, 232678853273148, 1310648830057380 (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) = 10*a(n-1) - 21*a(n-2) - 20*a(n-3) - 4*a(n-4) for n>5.

Empirical g.f.: 4*x*(4 - 13*x - 9*x^2 - 4*x^3 + 4*x^4) / (1 - 5*x - 2*x^2)^2. - Colin Barker, Jan 19 2019

EXAMPLE

Some solutions for n=4:

..0..0. .2..0. .2..2. .1..3. .3..2. .1..3. .2..2. .0..2. .3..2. .0..0

..1..1. .2..2. .3..0. .3..2. .2..3. .1..0. .0..3. .0..1. .1..3. .1..2

..1..0. .2..2. .1..1. .2..3. .2..2. .0..0. .1..1. .0..0. .1..1. .3..3

..2..0. .0..0. .1..0. .2..3. .0..2. .2..2. .3..3. .1..0. .3..3. .1..1

CROSSREFS

Column 2 of A269194.

Sequence in context: A260357 A056001 A163725 * A165558 A250425 A238171

Adjacent sequences:  A269185 A269186 A269187 * A269189 A269190 A269191

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 20 2016

STATUS

approved

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Last modified June 19 11:41 EDT 2019. Contains 324219 sequences. (Running on oeis4.)