A229374 Number of n X 2 0..2 arrays avoiding 11 horizontally, 22 vertically and 00 diagonally or antidiagonally.

8, 30, 126, 518, 2138, 8818, 36374, 150038, 618890, 2552850, 10530214, 43435926, 179168218, 739048370, 3048489846, 12574671318, 51869078378, 213954005138, 882535756294, 3640358873558, 15016063240250, 61939540321970

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