A269896 Number of n X 2 0..6 arrays with some element plus some horizontally or vertically adjacent neighbor totalling six exactly once.

7, 840, 45360, 2005080, 80724000, 3078006120, 113260615440, 4064194275960, 143136593671680, 4968778108446600, 170509976205204720, 5796622762505510040, 195530524142139886560, 6552338022044877818280, 218340123666185993749200

Offset

1,1

Links

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

Formula

Empirical: a(n) = 62*a(n-1) - 961*a(n-2) for n>3.

Conjectures from Colin Barker, Jan 29 2019: (Start)

G.f.: 7*x*(1 + 58*x + x^2) / (1 - 31*x)^2.

a(n) = 840 * 31^(n-3) * (23*n-15) for n>1.

(End)

Example

Some solutions for n=3:
..2..1. .1..5. .2..2. .2..4. .4..2. .3..5. .4..2. .3..6. .0..0. .4..3
..5..6. .4..6. .4..6. .6..1. .6..6. .3..4. .3..5. .4..2. .2..5. .5..1
..1..1. .1..6. .1..1. .6..3. .3..2. .6..3. .4..5. .1..6. .0..1. .4..3

Crossrefs

Column 2 of A269902.

Sequence in context: A047788 A251698 A203694 * A087350 A308296 A193342

Adjacent sequences: A269893 A269894 A269895 * A269897 A269898 A269899

Keyword

nonn

Author

R. H. Hardin, Mar 07 2016

Status

approved