A228501 Number of n X 3 binary arrays with top left value 1 and no two ones adjacent horizontally, vertically, diagonally or antidiagonally.

2, 3, 12, 29, 88, 239, 684, 1909, 5392, 15143, 42644, 119933, 337512, 949535, 2671740, 7517061, 21150272, 59508247, 167433188, 471090573, 1325464216, 3729333775, 10492879052, 29522830997, 83065631600, 233713998087, 657579228980

Offset: 1

Author

R. H. Hardin, Aug 23 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 3 of A228506.

Formula

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

Empirical g.f.: x*(2 - x) / (1 - 2*x - 3*x^2 + 2*x^3). - Colin Barker, Sep 11 2018