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A259217
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Number of (n+1) X (3+1) 0..1 arrays with each 2 X 2 subblock having clockwise pattern 0000 0011 or 0101.
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2
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24, 40, 66, 112, 192, 334, 588, 1048, 1890, 3448, 6360, 11854, 22308, 42352, 81042, 156160, 302736, 589966, 1154844, 2269096, 4472514, 8838760, 17505576, 34732942, 69015732, 137303104, 273427698, 544948528, 1086811680, 2168631118, 4329184620
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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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a(n) = 4*a(n-1) - 4*a(n-2) - a(n-3) + 2*a(n-4).
G.f.: 2*x*(12 - 28*x + x^2 + 16*x^3) / ((1 - x)*(1 - 2*x)*(1 - x - x^2)). - Colin Barker, Dec 24 2018
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EXAMPLE
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Some solutions for n=4:
..1..0..1..0....1..0..1..0....1..0..0..1....0..1..0..1....0..0..0..0
..0..1..0..1....0..1..0..1....0..1..1..0....1..0..1..0....1..1..1..1
..0..1..0..1....1..0..1..0....1..0..0..1....1..0..1..0....0..0..0..0
..0..1..0..1....0..1..0..1....0..1..1..0....1..0..1..0....0..0..0..0
..1..0..1..0....0..1..0..1....1..0..0..1....1..0..1..0....1..1..1..1
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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