A228678 Number of nX3 binary arrays with no two ones adjacent horizontally, diagonally or antidiagonally.

5, 19, 77, 313, 1277, 5215, 21305, 87049, 355685, 1453363, 5938613, 24265921, 99153677, 405154783, 1655515121, 6764650225, 27641241413, 112945711027, 461510880221, 1885793543785, 7705597945181, 31486076453887, 128656207802537

Offset

1,1

Comments

Column 3 of A228683

Links

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

Formula

Empirical: a(n) = 5*a(n-1) -3*a(n-2) -3*a(n-3).

Empirical: G.f. -x*(-5+6*x+3*x^2) / ( 1-5*x+3*x^2+3*x^3 ). - R. J. Mathar, Aug 31 2013

Example

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

Crossrefs

Sequence in context: A323269 A268815 A108981 * A149771 A149772 A370194

Adjacent sequences: A228675 A228676 A228677 * A228679 A228680 A228681

Keyword

nonn

Author

R. H. Hardin Aug 30 2013

Status

approved