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A189179
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Number of n X 2 array permutations with each element making a single king move.
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2
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1, 9, 33, 185, 913, 4777, 24577, 127385, 658801, 3410313, 17648609, 91343481, 472746833, 2446730345, 12663143361, 65538688857, 339198332209, 1755536122697, 9085854920609, 47024245778489, 243376070611729, 1259603657442857
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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) = 5*a(n-1) + 4*a(n-2) - 16*a(n-3).
Empirical g.f.: x*(1 + 4*x - 16*x^2) / (1 - 5*x - 4*x^2 + 16*x^3). - Colin Barker, Mar 01 2018
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EXAMPLE
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Some solutions for 3 X 2:
..1..0....1..2....2..0....2..0....1..0....1..2....3..0....2..3....3..2....3..0
..3..4....5..0....4..1....3..1....4..5....0..5....5..1....0..1....0..1....4..1
..5..2....3..4....5..3....5..4....2..3....3..4....2..4....5..4....5..4....5..2
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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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