A268634 Number of n X 3 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totalling two exactly once.

12, 120, 840, 5178, 29772, 163878, 875592, 4578186, 23548164, 119570574, 600870336, 2993807250, 14810051580, 72819229974, 356173467576, 1734202809114, 8410141924596, 40641730213278, 195782548631472, 940481337385122

Offset

1,1

Links

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

Formula

Empirical: a(n) = 10*a(n-1) - 29*a(n-2) + 20*a(n-3) - 4*a(n-4).

Empirical g.f.: 6*x*(2 - 2*x^2 + 3*x^3) / (1 - 5*x + 2*x^2)^2. - Colin Barker, Jan 14 2019

Example

Some solutions for n=6:
..0..0..0. .1..0..0. .1..0..0. .2..1..0. .0..1..2. .1..0..1. .1..0..0
..0..1..1. .0..1..0. .2..1..0. .1..0..0. .1..2..1. .0..1..0. .2..2..1
..0..0..0. .1..2..1. .1..0..0. .2..1..0. .2..2..1. .1..0..0. .2..1..0
..0..0..1. .2..2..2. .2..1..1. .2..0..0. .2..1..0. .2..1..0. .1..2..1
..0..1..0. .2..1..2. .1..2..2. .1..0..1. .1..2..1. .0..0..0. .2..2..2
..1..0..0. .0..0..1. .2..2..2. .2..1..0. .0..1..2. .0..0..0. .1..2..2

Crossrefs

Column 3 of A268639.

Sequence in context: A056311 A009050 A067358 * A061506 A059155 A012443

Adjacent sequences: A268631 A268632 A268633 * A268635 A268636 A268637

Keyword

nonn

Author

R. H. Hardin, Feb 09 2016

Status

approved