A228755 Number of 3 X n binary arrays with top left element equal to 1 and no two ones adjacent horizontally or antidiagonally.

4, 8, 39, 126, 482, 1712, 6277, 22700, 82580, 299648, 1088499, 3952186, 14352786, 52119040, 189266297, 687294648, 2495834292, 9063317432, 32912374319, 119517358582, 434013128786, 1576067091632, 5723300581661, 20783486354532

Offset: 1

Author

R. H. Hardin, Sep 02 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Row 3 of A228754.

Formula

Empirical: a(n) = 2*a(n-1) + 6*a(n-2) - a(n-4).

Empirical g.f.: x*(2 - x)*(2 + x) / (1 - 2*x - 6*x^2 + x^4). - Colin Barker, Sep 12 2018