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A269037 Number of 3 X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once. 1
0, 120, 348, 2166, 9528, 44760, 198816, 877800, 3809856, 16379232, 69769920, 295055136, 1239952512, 5183031744, 21564442752, 89355535680, 368925874944, 1518322209600, 6230763310464, 25503209969088, 104143201935360 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

Empirical: a(n) = 6*a(n-1) - a(n-2) - 28*a(n-3) - 4*a(n-4) + 16*a(n-5) - 4*a(n-6) for n>8.

Empirical g.f.: 6*x^2*(20 - 62*x + 33*x^2 + 40*x^3 - 3*x^4 - 16*x^5 + 4*x^6) / (1 - 3*x - 4*x^2 + 2*x^3)^2. - Colin Barker, Jan 18 2019

EXAMPLE

Some solutions for n=4:

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

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

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

CROSSREFS

Row 3 of A269035.

Sequence in context: A135805 A327912 A118058 * A144524 A052768 A242845

Adjacent sequences:  A269034 A269035 A269036 * A269038 A269039 A269040

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 18 2016

STATUS

approved

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Last modified July 12 16:03 EDT 2020. Contains 335665 sequences. (Running on oeis4.)