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A198976
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Number of n X 2 0..5 arrays with values 0..5 introduced in row major order and no element equal to any horizontal or vertical neighbor.
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3
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1, 4, 34, 481, 8731, 174454, 3603244, 75251971, 1577395861, 33105096904, 695065679254, 14595390246661, 306496273473391, 6436373295247354, 135163500079092064, 2838431127851480551, 59607037068329713321
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 32*a(n-1) - 262*a(n-2) + 672*a(n-3) - 441*a(n-4).
G.f.: x*(1 - 28*x + 168*x^2 - 231*x^3) / ((1 - x)*(1 - 3*x)*(1 - 7*x)*(1 - 21*x)).
a(n) = (189 + 56*3^n + 18*7^n + 21^n) / 504.
(End)
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EXAMPLE
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Some solutions with all values from 0 to 5 for n=4:
..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..2..3....2..3....2..3....2..3....2..3....2..3....2..3....2..0....2..0....2..0
..4..5....4..2....1..4....0..4....4..5....4..0....4..5....3..1....3..4....3..4
..2..0....0..5....0..5....2..5....1..2....0..5....0..4....4..5....5..2....0..5
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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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