A269761 Number of n X 2 0..5 arrays with some element plus some horizontally or vertically adjacent neighbor totalling five exactly once.

6, 480, 17520, 524160, 14288400, 368958240, 9195061680, 223482006720, 5331222081360, 125355762453600, 2913873085171440, 67100778335162880, 1533214659516235920, 34803572453875078560, 785602378216093258800

Offset

1,1

Links

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

Formula

Empirical: a(n) = 42*a(n-1) - 441*a(n-2) for n>3.

Conjectures from Colin Barker, Jan 28 2019: (Start)

G.f.: 6*x*(1 + 38*x + x^2) / (1 - 21*x)^2.

a(n) = 80 * 3^(n-2) * 7^(n-3) * (31*n-20) for n>1.

(End)

Example

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

Crossrefs

Column 2 of A269767.

Sequence in context: A220865 A080295 A084108 * A229503 A318634 A006713

Adjacent sequences: A269758 A269759 A269760 * A269762 A269763 A269764

Keyword

nonn

Author

R. H. Hardin, Mar 04 2016

Status

approved