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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. 2
16, 180, 1740, 15540, 132300, 1090740, 8787660, 69580980, 543538380, 4200069300, 32167589580, 244542858420, 1847388128460, 13880833735860, 103809654007500, 773174303047860, 5737767196302540, 42443199898890420, 313054205965641420 (list; graph; refs; listen; history; text; internal format)
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

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Last modified May 30 12:03 EDT 2020. Contains 334724 sequences. (Running on oeis4.)