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A269271 Number of n X 3 0..3 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling three exactly once. 1
24, 1368, 46872, 1365336, 36673560, 938176344, 23230366488, 561939624792, 13356872620056, 313173275509080, 7262896745936664, 166932248829835608, 3808216985895026712, 86327991673633618776, 1946351959512905208600 (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) = 42*a(n-1) - 441*a(n-2).

Conjectures from Colin Barker, Jan 20 2019: (Start)

G.f.: 24*x*(1 + 15*x) / (1 - 21*x)^2.

a(n) = 8*3^n * 7^(n-2) * (12*n-5).

(End)

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Column 3 of A269276.

Sequence in context: A068294 A003170 A160310 * A347857 A187852 A276595

Adjacent sequences:  A269268 A269269 A269270 * A269272 A269273 A269274

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 21 2016

STATUS

approved

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Last modified May 27 03:13 EDT 2022. Contains 354093 sequences. (Running on oeis4.)