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A204707
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Number of (n+1) X 3 0..1 arrays with the permanents of all 2 X 2 subblocks equal and nonzero.
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1
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13, 33, 81, 209, 529, 1361, 3473, 8913, 22801, 58449, 149649, 383441, 982033, 2515793, 6443921, 16507089, 42282769, 108311121, 277442193, 710686673, 1820455441, 4663202129, 11945023889, 30597832401, 78377927953, 200769257553
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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) = 2*a(n-1) +3*a(n-2) -4*a(n-3).
G.f.: x*(13 + 7*x - 24*x^2) / ((1 - x)*(1 - x - 4*x^2)).
a(n) = 1 + (2^(-1-n)*((1-sqrt(17))^n*(-19+5*sqrt(17)) + (1+sqrt(17))^n*(19+5*sqrt(17)))) / sqrt(17).
(End)
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EXAMPLE
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Some solutions for n=4:
..1..0..1....0..1..0....1..1..1....0..1..1....1..1..0....0..1..1....0..1..1
..1..1..1....1..1..1....0..1..0....1..0..1....0..1..1....1..1..0....1..0..1
..1..0..1....1..0..1....1..1..1....1..1..0....1..0..1....0..1..1....1..1..1
..1..1..1....0..1..0....1..0..1....0..1..1....1..1..0....1..1..0....1..0..1
..1..0..1....1..1..1....0..1..1....1..1..0....0..1..1....1..0..1....0..1..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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