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

1,1

Links

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

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

Example

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

Crossrefs

Row 3 of A228754.

Sequence in context: A032056 A214535 A321717 * A007215 A195677 A062753

Adjacent sequences: A228752 A228753 A228754 * A228756 A228757 A228758

Keyword

nonn

Author

R. H. Hardin, Sep 02 2013

Status

approved