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A231038 Number of 2 X n 0..2 arrays x(i,j) with each element horizontally, diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 3 and at least one element with value (x(i,j)-1) mod 3, and upper left element zero. 1
0, 0, 0, 4, 0, 32, 80, 560, 2080, 10720, 46496, 220896, 998432, 4634272, 21207840, 97791904, 449099040, 2066934176, 9501790240, 43707407520, 200983135008, 924361443232, 4250915450400, 19549937082016, 89907588137248 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

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

FORMULA

Empirical: a(n) = 3*a(n-1) + 6*a(n-2) + 32*a(n-4) - 20*a(n-5) + 24*a(n-6) - 16*a(n-7).

Empirical g.f.: 4*x^4*(1 - 3*x + 2*x^2 - 4*x^3) / (1 - 3*x - 6*x^2 - 32*x^4 + 20*x^5 - 24*x^6 + 16*x^7). - Colin Barker, Sep 25 2018

EXAMPLE

All solutions for n=4:

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

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

CROSSREFS

Row 2 of A231037.

Sequence in context: A270293 A270900 A123016 * A271280 A271086 A271292

Adjacent sequences:  A231035 A231036 A231037 * A231039 A231040 A231041

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 03 2013

STATUS

approved

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Last modified August 26 00:35 EDT 2019. Contains 326324 sequences. (Running on oeis4.)