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A136166
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a(n) = the number of divisors of n that are each not coprime to the previous or the following divisor of n.
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6
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0, 0, 0, 2, 0, 2, 0, 3, 2, 2, 0, 3, 0, 2, 2, 4, 0, 4, 0, 5, 2, 2, 0, 5, 2, 2, 3, 5, 0, 4, 0, 5, 2, 2, 2, 6, 0, 2, 2, 6, 0, 6, 0, 5, 3, 2, 0, 7, 2, 4, 2, 5, 0, 6, 2, 6, 2, 2, 0, 7, 0, 2, 3, 6, 2, 6, 0, 5, 2, 4, 0, 9, 0, 2, 4, 5, 2, 6, 0, 8, 4, 2, 0, 8, 2, 2, 2, 7, 0, 8, 2, 5, 2, 2, 2, 9, 0, 4, 5, 8, 0, 6, 0, 7, 4
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OFFSET
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1,4
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LINKS
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EXAMPLE
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The divisors of 28 are 1,2,4,7,14,28. Among adjacent pairs of divisors, 1 and 2 are coprime and 4 and 7 are coprime. Therefore there are a(28) =5 divisors that are each next to at least one divisor they are not coprime to. (These five divisors are 2,4,7,14,28.)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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