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A183702
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Number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock nonsingular.
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1
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192, 2472, 31800, 409128, 5263608, 67718760, 871232952, 11208812712, 144206530680, 1855283342568, 23869073504568, 307086608771880, 3950810460600312, 50828993677128552, 653938381502821560
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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) = 11*a(n-1) + 24*a(n-2).
G.f.: 24*x*(8 + 15*x) / (1 - 11*x - 24*x^2).
a(n) = (3*2^(-1-n)*((11-sqrt(217))^n*(-73+5*sqrt(217)) + (11+sqrt(217))^n*(73+5*sqrt(217)))) / sqrt(217).
(End)
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EXAMPLE
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Some solutions for 3 X 2:
..1..3....0..3....3..2....2..0....3..1....0..1....3..0....2..2....1..1....1..1
..2..3....2..3....3..0....3..1....3..3....2..1....0..3....1..3....2..3....2..0
..3..2....0..3....3..1....0..3....2..1....3..1....1..2....2..1....3..1....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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