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A269180 Number of n X 2 0..3 arrays with some element plus some horizontally, diagonally, antidiagonally or vertically adjacent neighbor totalling three exactly once. 1
4, 48, 384, 2736, 18336, 118032, 739008, 4533744, 27384288, 163381968, 965118720, 5654345136, 32898781728, 190290667152, 1095084877632, 6274151751024, 35807326610016, 203653219107408, 1154714957732736, 6529188836867376 (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*(1 - x)^2*(1 + 2*x)^2 / (1 - 5*x - 2*x^2)^2. - Colin Barker, Jan 19 2019

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 2 of A269186.

Sequence in context: A091904 A192831 A158681 * A228701 A111903 A059409

Adjacent sequences:  A269177 A269178 A269179 * A269181 A269182 A269183

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 20 2016

STATUS

approved

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Last modified July 18 19:00 EDT 2019. Contains 325144 sequences. (Running on oeis4.)