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A220997
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Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor.
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3
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3, 31, 306, 2989, 29135, 283872, 2765627, 26943707, 262494146, 2557299561, 24914003827, 242719929760, 2364652602239, 23037176752223, 224435298485050, 2186518067974709, 21301735038155095, 207528088736659200
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 11*a(n-1) - 11*a(n-2) - 12*a(n-3) - 2*a(n-4).
Empirical g.f.: x*(3 - 2*x - 2*x^2) / (1 - 11*x + 11*x^2 + 12*x^3 + 2*x^4). - Colin Barker, Feb 23 2018
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EXAMPLE
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Some solutions for n=3:
..2..1....3..0....1..1....0..2....0..2....0..1....1..1....3..0....0..1....0..1
..1..2....0..1....1..1....1..1....1..3....2..0....3..0....0..1....1..3....3..1
..0..0....1..1....0..2....1..1....0..0....1..2....1..0....2..0....0..1....1..0
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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