A207347 Number of 3 X n 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 0 and 1 1 1 vertically.

6, 36, 84, 192, 426, 858, 1704, 3330, 6390, 12150, 22938, 43044, 80424, 149766, 278160, 515568, 954072, 1763304, 3255666, 6006342, 11074116, 20407650, 37592934, 69228330, 127454070, 234605316, 431771328, 794539482, 1461954876, 2689788048

Offset: 1

Author

R. H. Hardin, Feb 17 2012

Keywords

• nonn

Comments

Row 3 of A207346.

Examples

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

Links

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

Crossrefs

Cf. A207346.

Formula

Empirical: a(n) = 2*a(n-1) + a(n-3) - 2*a(n-4) - a(n-5) - a(n-6) for n>7.

Empirical g.f.: 6*x*(1 + x)*(1 + 3*x - x^2 + 4*x^3 - x^4 + x^5) / ((1 - x - x^3)*(1 - x - x^2 - x^3)). - Colin Barker, Jun 22 2018