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A274890
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Number of n X 3 0..2 arrays with no element equal to any value at offset (0,-1) (-1,-1) or (-2,0) and new values introduced in order 0..2.
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1
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2, 12, 16, 38, 84, 192, 436, 990, 2253, 5121, 11645, 26483, 60215, 136936, 311381, 708076, 1610154, 3661438, 8326047, 18933223, 43053720, 97903198, 222629593, 506254676, 1151211539, 2617828789, 5952883022, 13536720098, 30782192928
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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) = a(n-1) + 4*a(n-2) - 6*a(n-4) - a(n-5) + 4*a(n-6) - a(n-8) for n>10.
Empirical g.f.: x*(2 + 10*x - 4*x^2 - 26*x^3 - 6*x^4 + 30*x^5 + 8*x^6 - 18*x^7 - x^8 + 4*x^9) / ((1 - x)*(1 + x)*(1 - x - 3*x^2 - x^3 + 3*x^4 - x^6)). - Colin Barker, Jan 31 2019
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EXAMPLE
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Some solutions for n=4:
..0..1..0. .0..1..2. .0..1..2. .0..1..2. .0..1..2. .0..1..0. .0..1..2
..2..1..2. .1..2..0. .0..1..0. .0..1..0. .1..2..0. .1..2..0. .0..1..2
..1..0..2. .1..2..1. .1..2..0. .1..2..0. .1..2..0. .1..0..1. .1..2..0
..1..0..1. .2..0..1. .2..0..1. .1..2..1. .2..0..1. .2..0..1. .1..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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