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

Author

R. H. Hardin, Sep 21 2013

Keywords

• nonn

Examples

			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
		

Links

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

Crossrefs

Column 2 of A229380.

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