A206981 Number of n X 2 0..1 arrays avoiding the patterns 0 1 0 or 1 0 1 in any row, column, diagonal or antidiagonal.

4, 16, 36, 100, 256, 676, 1764, 4624, 12100, 31684, 82944, 217156, 568516, 1488400, 3896676, 10201636, 26708224, 69923044, 183060900, 479259664, 1254718084, 3284894596, 8599965696, 22515002500, 58945041796, 154320122896, 404015326884

Offset: 1

Author

R. H. Hardin, Feb 14 2012

Keywords

• nonn

Examples

			Some solutions for n=4
..1..1....0..0....0..0....0..0....1..1....0..1....1..1....0..1....1..0....0..0
..0..1....0..1....1..0....1..0....1..1....1..1....1..1....1..0....0..1....1..1
..0..0....1..1....1..1....1..0....1..1....1..0....1..1....1..0....0..1....1..1
..1..0....1..1....0..1....1..0....1..1....1..0....0..0....1..0....1..0....0..0
		

Links

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

Crossrefs

Column 2 of A206987.

Cf. A080097.

Formula

Empirical: a(n) = 2*a(n-1) + 2*a(n-2) - a(n-3). G.f.: -4*x*(-1-2*x+x^2) / ( (1+x)*(x^2-3*x+1) ).

Empirical: a(n) = (A080097(n)+1)*4. - Martin Ettl, Nov 13 2012