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A183314
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Number of n X 2 binary arrays with an element zero only if there are an even number of ones to its left and an even number of ones above it.
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1
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3, 6, 13, 27, 57, 119, 250, 523, 1097, 2297, 4815, 10086, 21137, 44283, 92793, 194419, 407378, 853559, 1788481, 3747361, 7851867, 16451910, 34471669, 72228171, 151339401, 317100335, 664418698, 1392152131, 2916968489, 6111905849
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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) = a(n-1) + 3*a(n-2) - a(n-3) - a(n-4).
Empirical g.f.: x*(3 + 3*x - 2*x^2 - x^3) / (1 - x - 3*x^2 + x^3 + x^4). - Colin Barker, Mar 27 2018
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EXAMPLE
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Some solutions for 5 X 2.
..0..0....1..1....1..1....1..1....0..1....0..0....0..0....0..1....0..0....0..0
..0..0....1..1....1..1....1..1....0..1....0..1....0..1....0..1....0..0....0..1
..1..1....0..1....0..0....0..0....0..0....0..1....0..1....0..1....1..1....0..1
..1..1....0..1....0..1....0..0....1..1....0..1....0..0....0..1....1..1....1..1
..1..1....0..0....0..1....0..0....1..1....1..1....1..1....0..0....0..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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