A228684 Number of 3 X n binary arrays with no two ones adjacent horizontally, diagonally or antidiagonally.

8, 17, 77, 216, 809, 2529, 8832, 28793, 97933, 324464, 1092561, 3642241, 12217528, 40825697, 136745357, 457357256, 1531058169, 5122533089, 17144628912, 57369165513, 191993439053, 642478726624, 2150072260001, 7195049684481

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) - 5*a(n-3).

Empirical g.f.: x*(8 + x - 5*x^2) / (1 - 2*x - 6*x^2 + 5*x^3). - Colin Barker, Sep 12 2018

Example

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

Crossrefs

Row 3 of A228683.

Sequence in context: A186255 A244792 A187987 * A171065 A134790 A350683

Adjacent sequences: A228681 A228682 A228683 * A228685 A228686 A228687

Keyword

nonn

Author

R. H. Hardin, Aug 30 2013

Status

approved