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A269760 Number of n X 1 0..5 arrays with some element plus some horizontally or vertically adjacent neighbor totalling five exactly once. 2
0, 6, 60, 450, 3000, 18750, 112500, 656250, 3750000, 21093750, 117187500, 644531250, 3515625000, 19042968750, 102539062500, 549316406250, 2929687500000, 15563964843750, 82397460937500, 434875488281250 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 1 of A269767.

LINKS

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

FORMULA

Empirical: a(n) = 10*a(n-1) - 25*a(n-2).

Conjectures from Colin Barker, Mar 22 2018: (Start)

G.f.: 6*x^2 / (1 - 5*x)^2.

a(n) = 6*5^(n-2)*(n-1).

(End)

EXAMPLE

Some solutions for n=4:

..0. .2. .4. .2. .2. .5. .1. .0. .3. .1. .1. .5. .5. .2. .4. .0

..5. .3. .1. .5. .0. .1. .0. .4. .1. .1. .5. .0. .3. .4. .5. .0

..2. .3. .3. .0. .2. .4. .5. .2. .3. .4. .0. .3. .4. .1. .1. .5

..1. .0. .5. .0. .3. .5. .4. .3. .2. .0. .2. .3. .1. .1. .4. .3

CROSSREFS

Cf. A269767.

Sequence in context: A230842 A000911 A076100 * A043033 A179711 A061495

Adjacent sequences:  A269757 A269758 A269759 * A269761 A269762 A269763

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 04 2016

STATUS

approved

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Last modified January 18 12:00 EST 2021. Contains 340254 sequences. (Running on oeis4.)