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A221737
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Number of 2 X n arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without move-in move-out left turns.
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1
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1, 17, 152, 1347, 11917, 105408, 932331, 8246429, 72939328, 645145427, 5706285509, 50471867376, 446421650827, 3948581668413, 34925047119456, 308910646572419, 2732302328399893, 24167104943016272, 213757077778269179
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 15*a(n-1) - 67*a(n-2) + 120*a(n-3) - 80*a(n-4) + 10*a(n-5) for n>6.
Empirical g.f.: x*(1 + 2*x - 36*x^2 + 86*x^3 - 64*x^4 + 12*x^5) / (1 - 15*x + 67*x^2 - 120*x^3 + 80*x^4 - 10*x^5). - Colin Barker, Aug 10 2018
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EXAMPLE
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Some solutions for n=3:
..0..3..0....2..0..1....1..0..1....1..2..0....1..0..1....0..2..1....0..3..0
..1..1..1....1..2..0....1..3..0....0..2..1....2..2..0....0..3..0....2..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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