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A079531
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a(n) = phi(n) - ceiling(n^(2/3)).
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5
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0, -1, -1, -1, 1, -2, 2, 0, 1, -1, 5, -2, 6, 0, 1, 1, 9, -1, 10, 0, 4, 2, 13, -1, 11, 3, 9, 2, 18, -2, 20, 5, 9, 5, 13, 1, 24, 6, 12, 4, 28, -1, 29, 7, 11, 9, 32, 2, 28, 6, 18, 10, 37, 3, 25, 9, 21, 13, 42, 0, 44, 14, 20, 16, 31, 3, 49, 15, 27, 7, 52, 6, 54, 18, 22, 18, 41, 5, 59, 13, 35, 21, 62, 4, 44, 22
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OFFSET
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1,6
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COMMENTS
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a(n) >= 0 for n > 30.
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REFERENCES
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D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, p. 9.
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LINKS
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MATHEMATICA
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Table[EulerPhi[n]-Ceiling[Surd[n, 3]^2], {n, 90}] (* Harvey P. Dale, Oct 27 2016 *)
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PROG
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(Magma) [EulerPhi(n) - Ceiling(n^(2/3)): n in [1..100]]; // G. C. Greubel, Jan 14 2019
(Sage) [euler_phi(n) - ceil(n^(2/3)) for n in (1..100)] # G. C. Greubel, Jan 14 2019
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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