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A295091
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Number of n X 2 0..1 arrays with each 1 horizontally or vertically adjacent to 1 or 3 1s.
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4
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2, 5, 11, 24, 55, 123, 276, 621, 1395, 3134, 7043, 15825, 35558, 79899, 179531, 403402, 906437, 2036745, 4576524, 10283357, 23106493, 51919818, 116662773, 262138871, 589020696, 1323517491, 2973916807, 6682330408, 15015060133, 33738533867
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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) + 2*a(n-2) + 2*a(n-3) - a(n-5).
Empirical g.f.: x*(2 + 3*x + 2*x^2 - x^3 - x^4) / ((1 + x + x^2)*(1 - 2*x - x^2 + x^3)). - Colin Barker, Feb 21 2018
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EXAMPLE
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Some solutions for n=5:
..1..0. .1..1. .0..1. .1..0. .1..0. .1..1. .0..0. .0..0. .0..0. .0..0
..1..0. .0..0. .0..1. .1..0. .1..1. .0..0. .0..0. .1..0. .1..1. .0..0
..0..0. .0..1. .0..0. .0..0. .1..0. .1..0. .1..0. .1..1. .0..0. .1..0
..1..1. .0..1. .1..0. .1..0. .0..1. .1..1. .1..1. .1..0. .1..0. .1..0
..0..0. .0..0. .1..0. .1..0. .0..1. .1..0. .1..0. .0..0. .1..0. .0..0
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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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