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A240513
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Number of n X 2 0..1 arrays with no element equal to exactly two horizontal and vertical neighbors, with new values 0..1 introduced in row major order.
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23
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2, 3, 6, 10, 21, 42, 86, 179, 370, 770, 1601, 3330, 6930, 14419, 30006, 62442, 129941, 270410, 562726, 1171043, 2436962, 5071362, 10553601, 21962242, 45703842, 95110563, 197926886, 411889610, 857150101, 1783745642, 3712008566, 7724760339
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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) = 2*a(n-1) + a(n-2) - a(n-3) - 2*a(n-4) + a(n-5).
Empirical g.f.: x*(2 - x)*(1 - x^2 - 2*x^3) / ((1 - x)*(1 - x - 2*x^2 - x^3 + x^4)). - Colin Barker, Feb 24 2018
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EXAMPLE
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All solutions for n=4:
..0..1....0..1....0..1....0..1....0..0....0..1....0..1....0..1....0..1....0..1
..0..0....0..1....1..0....0..1....1..1....1..0....1..1....1..0....1..0....1..0
..0..1....1..0....1..1....1..0....0..0....1..0....0..1....0..1....0..0....0..1
..1..0....1..0....1..0....0..1....1..1....0..1....1..0....1..0....1..0....0..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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