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A189944
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1/4 the number of arrangements of n+1 nonzero numbers x(i) in -2..2 with the sum of sign(x(i))*(|x(i)| mod x(i+1)) equal to zero
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1
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3, 8, 22, 72, 280, 1152, 4632, 17888, 67232, 251136, 947136, 3625216, 14033664, 54599680, 212521344, 826308096, 3211280896, 12490338304, 48666153984, 189986959360, 742894424064, 2908269379584, 11394480500736, 44672464896000
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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: (n+1)*a(n) = 4*(2*n+1)*a(n-1) - 24*n*a(n-2) + 16*(2*n-1)*a(n-3). - Vaclav Kotesovec, Oct 19 2012
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EXAMPLE
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Some solutions with n=3
..2....2....2....1...-2...-2....1....2....2....1....2...-2...-2...-2...-1...-2
..2....2....2....2....2...-2...-2....2...-2....1....2....2....2...-2....2...-2
..2...-2...-2...-1...-1....1...-1...-1....2...-1...-2....2...-1....2....1...-1
..2...-1...-2....2....1....1....2....1...-2...-1....2...-2...-1....1....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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