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A269532
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Number of length-n 0..3 arrays with no repeated value differing from the previous repeated value by other than one.
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2
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4, 16, 60, 222, 804, 2878, 10192, 35812, 125012, 434110, 1500912, 5170626, 17758812, 60837880, 207965356, 709583398, 2417278172, 8223508510, 27943213944, 94853465148, 321696510276, 1090199408374, 3692112980824, 12496559933794
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 7*a(n-1) - 9*a(n-2) - 23*a(n-3) + 31*a(n-4) + 33*a(n-5).
Empirical g.f.: 2*x*(2 - 6*x - 8*x^2 + 19*x^3 + 17*x^4) / ((1 - 3*x)*(1 - 4*x - 3*x^2 + 14*x^3 + 11*x^4)). - Colin Barker, Mar 21 2018
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EXAMPLE
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Some solutions for n=9:
..2. .1. .0. .0. .3. .0. .1. .2. .1. .2. .0. .1. .1. .0. .0. .1
..1. .3. .3. .0. .0. .2. .2. .2. .0. .0. .3. .2. .3. .3. .2. .2
..0. .0. .2. .1. .3. .3. .0. .0. .3. .1. .0. .0. .1. .3. .0. .1
..2. .3. .2. .1. .2. .2. .1. .3. .1. .2. .0. .2. .0. .0. .3. .3
..2. .0. .3. .0. .0. .0. .0. .2. .0. .3. .2. .3. .3. .3. .2. .3
..3. .2. .0. .0. .3. .1. .0. .0. .2. .0. .3. .1. .3. .0. .0. .0
..1. .1. .3. .2. .2. .0. .3. .3. .2. .3. .2. .2. .1. .2. .1. .1
..1. .2. .0. .3. .3. .0. .1. .2. .0. .2. .1. .2. .2. .1. .2. .0
..3. .3. .3. .0. .0. .1. .3. .3. .3. .2. .2. .0. .2. .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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