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A275178
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Number of n X 3 0..2 arrays with no element equal to any value at offset (-2,-1) (-1,0) or (-1,1) and new values introduced in order 0..2.
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1
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5, 16, 25, 41, 85, 181, 389, 834, 1781, 3799, 8110, 17328, 37032, 79130, 169059, 361178, 771648, 1648657, 3522441, 7525825, 16079113, 34353402, 73396957, 156814715, 335039190, 715820740, 1529371036, 3267543982, 6981199507
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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) = 4*a(n-1) - 6*a(n-2) + 5*a(n-3) - a(n-4) - a(n-5) for n>8.
Empirical g.f.: x*(5 - 4*x - 9*x^2 + 12*x^3 - 4*x^4 - 17*x^5 + 11*x^6 + 5*x^7) / ((1 - x)*(1 - 3*x + 3*x^2 - 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..0..1. .0..0..1. .0..1..2. .0..0..1. .0..0..1. .0..0..0. .0..0..1
..2..2..0. .2..2..0. .2..0..1. .2..2..0. .2..2..2. .1..2..2. .2..2..0
..1..1..2. .0..1..2. .1..2..2. .0..1..1. .1..1..1. .0..1..1. .1..1..1
..0..0..1. .2..0..1. .0..0..1. .2..0..0. .2..0..0. .2..2..0. .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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