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A275498
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Number of n X 2 0..2 arrays with no element equal to any value at offset (-2,-1) (-2,0) or (-1,-1) and new values introduced in order 0..2.
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1
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2, 9, 16, 28, 56, 104, 200, 380, 724, 1380, 2628, 5008, 9540, 18176, 34628, 65972, 125688, 239456, 456204, 869144, 1655864, 3154696, 6010220, 11450468, 21815044, 41561284, 79181152, 150853252, 287400512, 547545732, 1043165604, 1987403816
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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) + 2*a(n-2) - a(n-4) for n>6.
Empirical g.f.: x*(2 + 7*x + 3*x^2 - 6*x^3 - 2*x^4 + x^5) / (1 - x - 2*x^2 + x^4). - Colin Barker, Feb 04 2019
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EXAMPLE
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Some solutions for n=4:
..0..1. .0..0. .0..0. .0..0. .0..1. .0..1. .0..1. .0..0. .0..0. .0..0
..1..1. .1..1. .1..1. .1..1. .1..1. .1..1. .1..1. .0..1. .0..1. .0..1
..2..2. .1..2. .1..2. .2..2. .2..2. .1..2. .1..2. .1..2. .1..2. .1..1
..0..0. .2..2. .2..0. .2..0. .2..0. .2..0. .0..0. .2..2. .1..2. .1..2
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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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