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A179211
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Number of squarefree numbers between n and 2*n (inclusive).
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8
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2, 2, 3, 3, 4, 4, 5, 5, 6, 7, 8, 8, 9, 8, 9, 9, 11, 11, 13, 13, 15, 15, 15, 15, 15, 16, 16, 17, 19, 19, 20, 19, 21, 21, 22, 22, 24, 23, 24, 24, 25, 25, 26, 26, 27, 28, 29, 29, 30, 30, 32, 32, 34, 34, 36, 36, 38, 38, 38, 38, 39, 39, 38, 39, 41, 41, 42, 41, 43, 43, 44, 44, 46, 45, 45
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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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MAPLE
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a := n -> nops(select(issqrfree, [$n..(2*n)])):
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MATHEMATICA
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a[n_] := Select[Range[n, 2n], SquareFreeQ] // Length;
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PROG
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(PARI) f(n)=my(s); forfactored(k=1, sqrtint(n), s += n\k[1]^2*moebius(k)); s
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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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