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A184679
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Number of (n+1) X 3 binary arrays with every 2 X 2 subblock singular.
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1
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28, 128, 544, 2384, 10384, 45392, 198352, 867152, 3791056, 16575056, 72469456, 316854608, 1385372368, 6057228368, 26483886544, 115794964304, 506288081104, 2213633766992, 9678629263312, 42317689343312, 185024841512656
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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) = 5*a(n-1) - 12*a(n-3).
G.f.: 4*x*(7 - 3*x - 24*x^2) / ((1 - 2*x)*(1 - 3*x - 6*x^2)).
a(n) = 2^(-2-n)*(11*2^(1+2*n) - 3*(3-sqrt(33))^n*(-55+7*sqrt(33)) + 3*(3+sqrt(33))^n*(55+7*sqrt(33))) / 11.
(End)
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EXAMPLE
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Some solutions for 5 X 3:
..0..0..1....1..0..1....1..0..1....0..0..0....0..0..1....0..0..0....0..0..1
..0..0..0....1..0..0....1..0..0....0..1..1....0..0..1....1..0..1....1..0..0
..0..0..1....0..0..0....0..0..0....0..0..0....0..0..1....0..0..1....0..0..0
..1..0..0....0..0..0....0..1..1....0..0..1....0..0..0....1..0..1....0..1..1
..1..0..0....0..0..0....0..0..0....1..0..1....1..0..1....1..0..0....0..0..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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