A207083 Number of n X 3 0..1 arrays avoiding 0 0 0 horizontally and 0 0 1 vertically.

7, 49, 241, 1117, 4891, 20953, 88465, 370753, 1546879, 6437929, 26754673, 111093277, 461065507, 1912995217, 7935844129, 32917778401, 136534855735, 566294540737, 2348729268913, 9741340873213, 40401894006955, 167564911503529

Offset: 1

Author

R. H. Hardin, Feb 15 2012

Keywords

• nonn

Comments

Column 3 of A207088.

Examples

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

Links

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

Crossrefs

Cf. A207088.

Formula

Empirical: a(n) = 6*a(n-1) - 5*a(n-2) - 14*a(n-3) + 11*a(n-4) + 4*a(n-5) - a(n-6).

Empirical g.f.: x*(7 + 7*x - 18*x^2 + 14*x^3 + 3*x^4 - x^5) / ((1 - x)*(1 - 2*x - x^2)*(1 - 3*x - 5*x^2 + x^3)). - Colin Barker, Jun 18 2018