A317809 Number of nX2 0..1 arrays with every element unequal to 0, 2 or 3 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.

1, 2, 2, 3, 5, 10, 23, 54, 131, 321, 789, 1943, 4788, 11802, 29094, 71725, 176826, 435938, 1074743, 2649629, 6532294, 16104471, 39703358, 97883171, 241317505, 594935145, 1466730843, 3616023336, 8914808626, 21978235610, 54184319689

Offset

1,2

Comments

Column 2 of A317815.

Links

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

Formula

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

Example

All solutions for n=5
..0..1. .0..1. .0..1. .0..1. .0..0
..1..0. .1..0. .1..0. .1..0. .0..0
..0..1. .1..0. .1..0. .0..1. .0..0
..0..1. .1..0. .0..1. .1..0. .0..0
..1..0. .0..1. .1..0. .0..1. .0..0

Crossrefs

Cf. A317815.

Sequence in context: A153900 A049873 A127180 * A249241 A089540 A080008

Adjacent sequences: A317806 A317807 A317808 * A317810 A317811 A317812

Keyword

nonn

Author

R. H. Hardin, Aug 07 2018

Status

approved