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A227747
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Number of n X 2 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X 3 binary array having determinant equal to one.
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1
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4, 13, 40, 129, 409, 1300, 4137, 13152, 41825, 133009, 422964, 1345045, 4277288, 13601889, 43254441, 137550436, 437414545, 1390991616, 4423395649, 14066532769, 44732002468, 142249129309, 452356561000, 1438507633089, 4574498058553
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = a(n-1) + 4*a(n-2) + 8*a(n-3) + 4*a(n-4) + a(n-5) - a(n-6).
Empirical g.f.: x*(4 + 9*x + 11*x^2 + 5*x^3 - x^5) / (1 - x - 4*x^2 - 8*x^3 - 4*x^4 - x^5 + x^6). - Colin Barker, Sep 09 2018
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EXAMPLE
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Some solutions for n=4:
..1..1....0..0....1..0....0..0....1..1....0..0....1..0....0..0....1..0....1..1
..0..1....0..0....0..1....0..0....0..0....1..1....0..1....0..0....1..1....0..1
..1..0....0..0....1..0....1..1....0..0....0..0....1..0....0..0....0..0....0..0
..1..1....0..1....0..1....0..0....0..0....1..0....1..0....1..0....0..1....1..0
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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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