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A269584
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Number of length-4 0..n arrays with no repeated value differing from the previous repeated value by more than one.
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1
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16, 79, 250, 613, 1276, 2371, 4054, 6505, 9928, 14551, 20626, 28429, 38260, 50443, 65326, 83281, 104704, 130015, 159658, 194101, 233836, 279379, 331270, 390073, 456376, 530791, 613954, 706525, 809188, 922651, 1047646, 1184929, 1335280
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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^4 + 4*n^3 + 5*n^2 + 5*n + 1.
G.f.: x*(16 - x + 15*x^2 - 7*x^3 + x^4) / (1 - x)^5.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5.
(End)
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EXAMPLE
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Some solutions for n=6:
..4. .0. .1. .6. .0. .1. .1. .2. .1. .3. .5. .1. .2. .3. .0. .6
..0. .5. .3. .4. .3. .5. .2. .1. .2. .2. .2. .3. .5. .4. .6. .2
..1. .6. .0. .1. .6. .4. .1. .1. .5. .6. .4. .1. .3. .0. .2. .2
..2. .6. .4. .0. .4. .1. .5. .0. .0. .0. .3. .0. .2. .5. .2. .0
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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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