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A241073
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Number of n X 2 0..2 arrays with no element equal to exactly one horizontal or vertical neighbor, with new values 0..2 introduced in row major order.
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1
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1, 4, 12, 39, 131, 444, 1516, 5195, 17847, 61424, 211672, 730119, 2520091, 8702628, 30063396, 103881123, 359017439, 1240945016, 4289745552, 14829991071, 51271047939, 177263517036, 612883590684, 2119068084731, 7326858673287
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OFFSET
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1,2
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LINKS
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FORMULA
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Empirical: a(n) = 6*a(n-1) - 8*a(n-2) - 4*a(n-3) + a(n-4) + 14*a(n-5) - 8*a(n-6) for n>7.
Empirical g.f.: x*(1 + x)*(1 - 3*x - x^2 + 4*x^3 + 4*x^4 - 4*x^5) / ((1 - x)*(1 - 5*x + 3*x^2 + 7*x^3 + 6*x^4 - 8*x^5)). - Colin Barker, Oct 29 2018
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EXAMPLE
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Some solutions for n=4:
..0..1....0..1....0..1....0..1....0..0....0..0....0..1....0..1....0..0....0..0
..2..0....2..0....1..2....1..2....0..0....0..0....1..2....1..0....0..0....0..0
..1..2....0..2....2..1....0..1....0..0....0..0....2..0....0..1....1..1....1..2
..2..0....2..1....1..2....2..0....1..2....0..0....1..2....1..0....1..1....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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