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A269103

Number of n X 2 0..3 arrays with some element plus some horizontally or vertically adjacent neighbor totalling three no more than once.

16, 180, 1740, 15540, 132300, 1090740, 8787660, 69580980, 543538380, 4200069300, 32167589580, 244542858420, 1847388128460, 13880833735860, 103809654007500, 773174303047860, 5737767196302540, 42443199898890420, 313054205965641420

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OFFSET

1,1

COMMENTS

Column 2 of A269109.

LINKS

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

FORMULA

Empirical: a(n) = 14*a(n-1) - 49*a(n-2) for n>3.

Conjectures from Colin Barker, Mar 21 2018: (Start)

G.f.: 4*x*(4 - 11*x + x^2) / (1 - 7*x)^2.

a(n) = 60*7^(n-3)*(8*n+5) for n>1.

(End)

EXAMPLE

Some solutions for n=4:

..2..2. .2..0. .2..2. .1..0. .3..3. .3..1. .1..3. .3..1. .1..3. .1..0

..0..2. .2..0. .2..3. .3..1. .3..1. .3..3. .3..1. .3..1. .1..3. .3..1

..1..0. .0..2. .2..3. .1..1. .2..2. .2..2. .3..3. .1..3. .0..1. .0..1

..1..0. .1..0. .1..1. .1..1. .3..3. .3..0. .1..3. .3..1. .0..0. .2..0

CROSSREFS

Cf. A269109.

Sequence in context: A021084 A227557 A269202 * A016305 A218895 A016909

Adjacent sequences: A269100 A269101 A269102 * A269104 A269105 A269106

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 19 2016

STATUS

approved

URL: https://oeis.org/A269103

⇱ A269103 - OEIS