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 A079532 a(n) = floor(n - sqrt(n)) - phi(n). 4
 -1, -1, -1, 0, -2, 1, -2, 1, 0, 2, -3, 4, -3, 4, 3, 4, -4, 7, -4, 7, 4, 7, -4, 11, 0, 8, 3, 10, -5, 16, -5, 10, 7, 12, 5, 18, -6, 13, 8, 17, -6, 23, -6, 17, 14, 17, -6, 25, 0, 22, 11, 20, -7, 28, 7, 24, 13, 22, -7, 36, -7, 24, 19, 24, 8, 37, -8, 27, 16, 37, -8, 39, -8, 29, 26, 31, 8, 45, -8, 39, 18, 32, -9, 50, 11, 34 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS a(n) >= 0 if n is composite. a(n) = 0 if n is the square of a prime (see A001248). - Michel Lagneau, May 25 2012 REFERENCES D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, p. 9. W. Sierpiński, Elementary Theory of Numbers. Państ. Wydaw. Nauk., Warsaw, 1964. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 W. Sierpiński, Elementary Theory of Numbers, Warszawa 1964. MATHEMATICA Table[Floor[n - Sqrt[n]] - EulerPhi[n], {n, 100}] (* Vincenzo Librandi, Dec 13 2014 *) PROG (PARI) vector(100, n, floor(n - sqrt(n)) - eulerphi(n)) \\ Michel Marcus, Dec 12 2014 (MAGMA) [Floor(n - Sqrt(n)) - EulerPhi(n): n in [1..100]]; // Vincenzo Librandi, Dec 13 2014 (Sage) [floor(n-sqrt(n)) - euler_phi(n) for n in (1..100)] # G. C. Greubel, Jan 14 2019 CROSSREFS Cf. A000010, A079530, A079531, A079533, A079534. Sequence in context: A236831 A030205 A159817 * A328176 A191312 A240159 Adjacent sequences:  A079529 A079530 A079531 * A079533 A079534 A079535 KEYWORD sign AUTHOR N. J. A. Sloane, Jan 23 2003 STATUS approved

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Last modified December 5 13:26 EST 2019. Contains 329751 sequences. (Running on oeis4.)