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A276300
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Number of 3 X n 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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5, 11, 45, 173, 693, 2765, 11061, 44237, 176949, 707789, 2831157, 11324621, 45298485, 181193933, 724775733, 2899102925, 11596411701, 46385646797, 185542587189, 742170348749, 2968681394997, 11874725579981, 47498902319925
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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) + a(n-2) - 4*a(n-3) for n>4.
G.f.: x*(5 - 9*x - 4*x^2 + 2*x^3) / ((1 - x)*(1 + x)*(1 - 4*x)).
a(n) = (8 + 27*4^n) / 40 for n>1 and even.
a(n) = (72 + 27*4^n) / 40 for n>1 and odd.
(End)
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EXAMPLE
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Some solutions for n=4:
..0..1..2..1. .0..1..0..1. .0..1..0..1. .0..1..0..2. .0..1..2..1
..0..1..2..0. .0..2..0..1. .2..1..2..1. .0..2..1..2. .0..1..2..0
..2..1..2..0. .0..2..0..2. .2..1..0..2. .1..2..0..2. .0..1..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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