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A269471
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Number of length-7 0..n arrays with no repeated value equal to the previous repeated value.
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1
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30, 1206, 11796, 63420, 242370, 741090, 1934856, 4488696, 9499590, 18678990, 34580700, 60879156, 102703146, 167030010, 263145360, 403173360, 602682606, 881372646, 1263846180, 1780471980, 2468343570, 3372338706, 4546284696
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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) = n^7 + 7*n^6 + 16*n^5 + 8*n^4 - n^3 - n.
G.f.: 6*x*(5 + 161*x + 498*x^2 + 190*x^3 - 23*x^4 + 9*x^5) /(1 - x)^8.
a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>8.
(End)
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EXAMPLE
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Some solutions for n=3:
..2. .0. .0. .0. .1. .1. .0. .0. .0. .1. .3. .0. .2. .3. .3. .0
..0. .2. .2. .3. .2. .3. .1. .2. .2. .2. .2. .1. .1. .3. .3. .1
..2. .2. .1. .0. .2. .1. .3. .2. .2. .2. .3. .0. .1. .1. .0. .3
..3. .0. .2. .3. .0. .2. .2. .0. .3. .3. .0. .2. .3. .0. .1. .0
..1. .1. .3. .2. .0. .3. .2. .0. .3. .2. .1. .2. .2. .2. .1. .0
..0. .1. .2. .0. .2. .3. .0. .1. .2. .3. .3. .3. .2. .1. .2. .3
..3. .2. .3. .1. .1. .2. .0. .0. .1. .1. .2. .1. .3. .3. .2. .3
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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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