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A268943
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Number of length-n 0..7 arrays with no repeated value unequal to the previous repeated value plus one mod 7+1.
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1
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8, 64, 504, 3928, 30344, 232696, 1773384, 13443064, 101433800, 762265720, 5707893576, 42605289208, 317113497800, 2354253598072, 17437541654088, 128885063291896, 950791205063624, 7001691181273720, 51477520840048968
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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) = 13*a(n-1) - 34*a(n-2) - 56*a(n-3).
G.f.: 8*x*(1 - 5*x - 7*x^2) / ((1 - 7*x)*(1 - 6*x - 8*x^2)).
a(n) = (-272*7^n + (153-37*sqrt(17))*(3-sqrt(17))^n + (3+sqrt(17))^n*(153+37*sqrt(17))) / 34.
(End)
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EXAMPLE
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Some solutions for n=5:
..0. .7. .3. .6. .2. .5. .7. .0. .1. .2. .2. .0. .6. .3. .5. .7
..7. .6. .5. .7. .1. .2. .7. .5. .1. .1. .4. .5. .4. .3. .5. .5
..2. .3. .5. .6. .0. .0. .3. .5. .2. .3. .7. .2. .3. .1. .2. .6
..1. .2. .0. .5. .3. .7. .5. .1. .0. .5. .5. .4. .5. .5. .5. .1
..1. .0. .3. .3. .3. .0. .6. .5. .7. .1. .3. .4. .4. .6. .4. .6
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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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