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A229374 Number of n X 2 0..2 arrays avoiding 11 horizontally, 22 vertically and 00 diagonally or antidiagonally. 1
8, 30, 126, 518, 2138, 8818, 36374, 150038, 618890, 2552850, 10530214, 43435926, 179168218, 739048370, 3048489846, 12574671318, 51869078378, 213954005138, 882535756294, 3640358873558, 15016063240250, 61939540321970 (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) = 4*a(n-1) + a(n-2) - 2*a(n-3).

Empirical g.f.: 2*x*(4 - x - x^2) / (1 - 4*x - x^2 + 2*x^3). - Colin Barker, Sep 14 2018

EXAMPLE

Some solutions for n=4:

  1 0   1 0   1 2   0 2   2 1   1 0   0 1   2 0   0 1   0 1

  1 2   2 2   2 0   2 1   0 1   2 1   2 1   1 2   1 2   2 1

  0 1   0 1   1 2   0 1   2 1   0 0   0 0   2 1   0 1   0 1

  0 1   1 2   0 1   0 1   1 0   1 2   2 2   0 0   1 2   0 1

CROSSREFS

Column 2 of A229380.

Sequence in context: A055737 A293965 A161222 * A215471 A221145 A098741

Adjacent sequences:  A229371 A229372 A229373 * A229375 A229376 A229377

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 21 2013

STATUS

approved

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Last modified September 25 11:10 EDT 2022. Contains 356984 sequences. (Running on oeis4.)