A228798 Number of 3 X n binary arrays with top left element equal to 1 and no two ones adjacent horizontally or nw-se.

4, 5, 36, 97, 411, 1394, 5223, 18708, 68348, 247545, 899960, 3266477, 11864371, 43080054, 156446379, 568106600, 2063027108, 7491613757, 27204943788, 98791463513, 358749562651, 1302756292618, 4730805017359, 17179356326908

Offset

1,1

Links

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

Formula

Empirical: a(n) = a(n-1) + 8*a(n-2) + 6*a(n-3) - a(n-4) - a(n-5).

Empirical g.f.: x*(4 + x - x^2 - 3*x^3) / ((1 + x)*(1 - 2*x - 6*x^2 + x^4)). - Colin Barker, Sep 13 2018

Example

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

Crossrefs

Row 3 of A228796.

Sequence in context: A131139 A152291 A336024 * A041557 A270087 A265689

Adjacent sequences: A228795 A228796 A228797 * A228799 A228800 A228801

Keyword

nonn

Author

R. H. Hardin, Sep 04 2013

Status

approved