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 A079531 a(n) = phi(n) - ceiling(n^(2/3)). 5
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 COMMENTS a(n) >= 0 for n > 30. REFERENCES D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, p. 9. LINKS G. C. Greubel, Table of n, a(n) for n = 1..10000 MATHEMATICA Table[EulerPhi[n]-Ceiling[Surd[n, 3]^2], {n, 90}] (* Harvey P. Dale, Oct 27 2016 *) PROG (PARI) a(n)=eulerphi(n)-sqrtnint(n^2-1, 3)-1 \\ Charles R Greathouse IV, Feb 07 2013 (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 CROSSREFS Cf. A000010, A079530, A079532, A079534. Sequence in context: A174626 A264909 A104579 * A182882 A134178 A059018 Adjacent sequences:  A079528 A079529 A079530 * A079532 A079533 A079534 KEYWORD sign,easy AUTHOR N. J. A. Sloane, Jan 23 2003 STATUS approved

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Last modified December 11 07:47 EST 2019. Contains 329914 sequences. (Running on oeis4.)