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A221297
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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, with no occupancy greater than 2.
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2
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3, 19, 137, 1001, 7305, 53291, 388741, 2835697, 20685009, 150886255, 1100633309, 8028513089, 58563541437, 427188362291, 3116100301045, 22730208012457, 165804141741249, 1209448362939775, 8822248421700605, 64353360753783545
(list;
graph;
refs;
listen;
history;
text;
internal format)
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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) - 27*a(n-2) - a(n-3) + 8*a(n-4) - 16*a(n-5) - 6*a(n-6) + 2*a(n-7).
Empirical g.f.: x*(3 - 14*x + 9*x^2 + 10*x^3 - 12*x^4 - 4*x^5 + 2*x^6) / (1 - 11*x + 27*x^2 + x^3 - 8*x^4 + 16*x^5 + 6*x^6 - 2*x^7). - Colin Barker, Mar 14 2018
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EXAMPLE
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Some solutions for n=3:
..1..1....0..1....1..0....1..2....2..0....2..0....2..1....1..1....1..2....2..2
..0..1....2..0....2..2....2..0....2..0....2..0....1..0....2..0....0..2....0..0
..2..1....2..1....0..1....1..0....0..2....2..0....0..2....1..1....1..0....1..1
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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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