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A270112 Number of n X 2 0..7 arrays with some element plus some horizontally or vertically adjacent neighbor totalling seven exactly once. 1
8, 1344, 100800, 6183744, 345422784, 18272616768, 932758314432, 46431146637120, 2268408487407552, 109231939785014592, 5199659528294691264, 245200862770851468096, 11473103730476342109120, 533310525557661056874816 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 86*a(n-1) - 1849*a(n-2) for n>3.

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

G.f.: 8*x*(1 + 82*x + x^2) / (1 - 43*x)^2.

a(n) = 1344*43^(n-3) * (32*n-21) for n>1.

(End)

EXAMPLE

Some solutions for n=3:

..0..1. .1..5. .4..5. .5..6. .2..5. .7..0. .2..0. .7..7. .4..0. .3..1

..0..3. .5..4. .3..7. .1..4. .2..4. .4..6. .2..3. .2..0. .6..7. .4..5

..7..5. .1..3. .0..3. .1..3. .1..2. .5..5. .5..0. .6..2. .6..5. .7..5

CROSSREFS

Column 2 of A270118.

Sequence in context: A017187 A168575 A286315 * A281127 A001418 A123268

Adjacent sequences:  A270109 A270110 A270111 * A270113 A270114 A270115

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 11 2016

STATUS

approved

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Last modified September 26 03:40 EDT 2022. Contains 356986 sequences. (Running on oeis4.)