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A209726
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1/4 the number of (n+1) X 8 0..2 arrays with every 2 X 2 subblock having distinct clockwise edge differences.
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1
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16, 17, 18, 20, 22, 26, 30, 38, 46, 62, 78, 110, 142, 206, 270, 398, 526, 782, 1038, 1550, 2062, 3086, 4110, 6158, 8206, 12302, 16398, 24590, 32782, 49166, 65550, 98318, 131086, 196622, 262158, 393230, 524302, 786446, 1048590, 1572878, 2097166
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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) = a(n-1) + 2*a(n-2) - 2*a(n-3).
G.f.: x*(16 + x - 31*x^2) / ((1 - x)*(1 - 2*x^2)).
a(n) = 3*2^(n/2 - 1) + 14 for n even.
a(n) = 2^((n + 1)/2) + 14 for n odd.
(End)
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EXAMPLE
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Some solutions for n=4:
..1..2..0..2..1..2..0..2....0..1..0..2..0..1..0..2....1..2..0..2..0..2..1..2
..2..0..1..0..2..0..1..0....2..0..2..1..2..0..2..1....2..0..1..0..1..0..2..0
..1..2..0..2..1..2..0..2....0..1..0..2..0..1..0..2....1..2..0..2..0..2..1..2
..2..0..1..0..2..0..1..0....2..0..2..1..2..0..2..1....2..0..1..0..1..0..2..0
..1..2..0..2..1..2..0..2....0..1..0..2..0..1..0..2....1..2..0..2..0..2..1..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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