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A304573
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Number of non-perfect powers (A007916) less than n and relatively prime to n.
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3
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0, 0, 1, 1, 2, 1, 4, 3, 3, 2, 6, 3, 8, 4, 5, 6, 11, 5, 13, 6, 8, 8, 17, 7, 15, 9, 13, 8, 21, 7, 23, 12, 14, 12, 17, 10, 27, 14, 18, 13, 31, 10, 33, 16, 19, 18, 37, 14, 33, 16, 25, 19, 42, 15, 31, 20, 29, 23, 48, 14, 50, 25, 30, 27, 38, 17, 55, 27, 36, 21, 59
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OFFSET
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1,5
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LINKS
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EXAMPLE
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The a(21) = 8 positive integers less than and relatively prime to 21 that are not perfect powers are {2, 5, 10, 11, 13, 17, 19, 20}.
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MATHEMATICA
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Table[Length[Select[Range[2, n], And[GCD@@FactorInteger[#][[All, 2]]==1, GCD[n, #]==1]&]], {n, 50}]
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PROG
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(PARI) a(n) = sum(k=2, n-1, !ispower(k) && (gcd(n, k) == 1)); \\ Michel Marcus, May 15 2018
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CROSSREFS
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Cf. A000005, A000010, A000961, A001597, A005117, A007916, A008683, A073311, A139555, A304326, A304362, A304574, A304575, A304576.
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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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