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A221689
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Number of n X 3 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without consecutive moves in the same direction.
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1
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6, 152, 3112, 63676, 1302720, 26650988, 545221260, 11154026300, 228186749552, 4668196767064, 95500991265668, 1953739262283024, 39969188300499044, 817681276128120100, 16727952148700884996, 342216938625170086928
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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) = 24*a(n-1) - 69*a(n-2) - 71*a(n-3) + 2*a(n-4) for n>5.
Empirical g.f.: 2*x*(3 + 4*x - 61*x^2 - 49*x^3 + 2*x^4) / (1 - 24*x + 69*x^2 + 71*x^3 - 2*x^4). - Colin Barker, Aug 10 2018
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EXAMPLE
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Some solutions for n=3:
..0..4..0....0..3..0....0..2..1....0..2..2....0..3..1....1..1..1....1..2..0
..1..0..0....1..1..0....0..1..0....0..1..0....0..1..0....1..1..0....1..2..1
..1..1..2....2..2..0....2..1..2....1..1..2....2..1..1....0..4..0....0..2..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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