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A206857
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Number of n X 2 0..2 arrays avoiding the pattern z z+1 z in any row, column, diagonal or antidiagonal.
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4
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9, 81, 625, 4761, 36481, 279841, 2146225, 16459249, 126225225, 968018769, 7423717921, 56932346025, 436613028289, 3348376640449, 25678633973281, 196928934060769, 1510244084935881, 11582031898782801, 88822372650180625
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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) = 8*a(n-1) -5*a(n-2) +18*a(n-3) +7*a(n-4) -2*a(n-5) -a(n-6).
Empirical g.f.: x*(9 + 9*x + 22*x^2 + 4*x^3 - 3*x^4 - x^5) / ((1 - x + 3*x^2 - x^3)*(1 - 7*x - 5*x^2 - x^3)). - Colin Barker, Feb 20 2018
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EXAMPLE
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Some solutions for n=4:
..1..0....0..2....0..2....0..1....2..0....0..2....0..2....2..1....0..2....2..1
..1..1....2..2....0..0....2..1....1..2....0..2....1..1....2..1....0..1....0..2
..0..1....0..0....0..1....2..0....0..2....2..2....2..0....2..2....2..0....1..2
..2..0....2..1....2..1....0..1....2..0....0..2....0..1....1..2....1..0....2..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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