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A275222
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Number of n X 2 0..2 arrays with no element equal to any value at offset (-2,-1) (-2,1) or (-1,0) and new values introduced in order 0..2.
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1
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2, 6, 11, 27, 66, 162, 404, 1007, 2512, 6271, 15655, 39084, 97580, 243626, 608259, 1518638, 3791579, 9466427, 23634810, 59008986, 147327628, 367832623, 918367048, 2292885359, 5724642759, 14292705300, 35684571668, 89093606034, 222439846275
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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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Empirical: a(n) = 3*a(n-1) - a(n-2) - 2*a(n-4) + a(n-5) for n>6.
Empirical g.f.: x*(1 + x - x^2)*(2 - 2*x - x^2 - x^3) / ((1 - x)*(1 - 2*x - x^2 - x^3 + x^4)). - Colin Barker, Feb 01 2019
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EXAMPLE
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Some solutions for n=4:
..0..1. .0..0. .0..1. .0..1. .0..1. .0..1. .0..0. .0..1. .0..1. .0..1
..1..0. .1..2. .1..0. .1..0. .2..0. .1..0. .1..2. .1..2. .1..0. .2..0
..2..2. .2..1. .0..2. .2..1. .0..2. .0..1. .2..1. .2..1. .0..2. .0..1
..1..0. .1..2. .2..0. .1..2. .1..1. .1..2. .0..0. .1..2. .1..0. .2..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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