A184755 Half the number of n X 3 binary arrays with no 1 having an adjacent 1 both above and to its left.

4, 25, 163, 1056, 6847, 44391, 287802, 1865917, 12097367, 78431296, 508496451, 3296753387, 21373960178, 138574567177, 898425491035, 5824794400480, 37764099690423, 244837350020575, 1587362824918602, 10291406673539877

Offset: 1

Author

R. H. Hardin, Jan 21 2011

Keywords

• nonn

Comments

Column 3 of A184761.

Examples

			Some solutions for 5 X 3:
..0..1..0....1..0..1....1..1..0....1..0..0....0..0..0....0..1..1....1..1..0
..0..1..0....1..0..1....1..0..0....0..1..0....1..1..1....1..0..0....1..0..1
..0..1..0....1..0..1....0..1..0....0..0..1....1..0..0....0..1..1....0..1..0
..0..1..0....1..0..1....0..1..0....0..0..0....1..0..0....1..0..0....0..0..0
..0..0..0....1..0..0....1..0..0....0..1..0....1..1..1....1..0..1....1..1..0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A184761.

Formula

Empirical: a(n) = 5*a(n-1) + 9*a(n-2) + 4*a(n-3).

Empirical g.f.: x*(4 + 5*x + 2*x^2) / (1 - 5*x - 9*x^2 - 4*x^3). - Colin Barker, Apr 14 2018