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A264840
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Consider the sequence {3k, k >= 1}, and write down the numbers of consecutive terms that are squarefree.
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2
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2, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1
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OFFSET
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1,1
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COMMENTS
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This is a (1,2)-sequence (every term is either 1 or 2), since out of every three consecutive multiples of 3 at least one is not squarefree (it is divisible by 9).
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LINKS
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EXAMPLE
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The multiples of 3 are 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, .... The squarefree ones are (3,6), (15), (21), (30,33), .... So a(1)=2, a(2)=1, a(3)=1, a(4)=2, ....
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MATHEMATICA
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Map[Count[#, True]&, DeleteCases[Split[Map[SquareFreeQ[3#]&, Range[400]]], {___, False, ___}]] (* Peter J. C. Moses, Nov 26 2015 *)
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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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