A079534 - OEIS

%I #8 Sep 08 2022 08:45:08

%S 0,1,1,2,0,4,2,4,2,8,2,10,4,6,6,13,3,15,5,9,7,19,5,17,9,15,9,25,4,26,

%T 12,16,12,20,8,32,14,20,12,36,8,38,15,19,17,41,11,37,15,27,19,47,13,

%U 35,19,31,23,52,10,54,24,30,26,42,14,60,26,38,18,64,18,66,30,33,29,53,17,71,25

%N a(n) = phi(n) - ceiling( (log 2 / 2) * (n / log n) ).

%C It is known that a(n) >= 0.

%D D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, p. 9.

%H G. C. Greubel, <a href="/A079534/b079534.txt">Table of n, a(n) for n = 2..10000</a>

%t Table[EulerPhi[n] - Ceiling[n*Log[2.]/(2*Log[n])], {n, 2, 80}] (* _G. C. Greubel_, Jan 14 2019 *)

%o (PARI) vector(80, n, n++; eulerphi(n) - ceil(n*log(2.)/(2*log(n)))) \\ _G. C. Greubel_, Jan 14 2019

%o (Magma) [EulerPhi(n) - Ceiling(n*Log(2.)/(2*Log(n))): n in [2..80]]; // _G. C. Greubel_, Jan 14 2019

%o (Sage) [euler_phi(n) - ceil(n*log(2.)/(2*log(n))) for n in (2..80)] # _G. C. Greubel_, Jan 14 2019

%Y Cf. A000010, A079530, A079531, A079532, A079533.

%K nonn

%O 2,4

%A _N. J. A. Sloane_, Jan 23 2003