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A276293
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Number of n X 2 0..2 arrays with no element equal to any value at offset (-2,-1) (-1,1) or (0,-1) and new values introduced in order 0..2.
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1
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1, 4, 11, 31, 88, 250, 710, 2016, 5724, 16252, 46144, 131016, 371992, 1056192, 2998832, 8514544, 24175232, 68640416, 194889824, 553348096, 1571113920, 4460842944, 12665612288, 35961305216, 102104457600, 289903834112
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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) = 4*a(n-1) - 4*a(n-2) + 2*a(n-3) for n>4.
Empirical g.f.: x*(1 - x^2 + x^3) / (1 - 4*x + 4*x^2 - 2*x^3). - Colin Barker, Feb 05 2019
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EXAMPLE
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Some solutions for n=4:
..0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1
..0..2. .2..1. .0..1. .0..2. .2..0. .0..2. .0..1. .0..1. .0..1. .2..1
..0..1. .2..1. .0..2. .0..1. .1..2. .0..2. .2..1. .0..2. .0..1. .2..1
..0..2. .0..1. .0..1. .0..1. .0..1. .0..2. .2..1. .1..2. .0..2. .2..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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