A306371 - OEIS

%I #8 Feb 17 2019 20:48:26

%S 1,2,4,6,8,12,16,20,24,32,36,40,48,64,72,80,96,120,144,160,176,200,

%T 216,240,288,320,336,384,432,448,480,576,720,768,880,960,1056,1200,

%U 1280,1344,1440,1664,1680,1728,1920,2112,2208,2304,2400,2592,2784,2880,3072,3456,3840,4224,4320

%N Number of primitive roots of prime A103521(n).

%C Numbers k in A008330 such that no numbers <= k occur later than k in A008330.

%C Different from A036912 since a(19) = 144 and A036912(19) = 128.

%F a(n) = phi(A103521(n)-1).

%o (PARI) b(n) = if(n==1, 2, floor(exp(Euler)*n*log(log(n^2))+2.5*n/log(log(n^2))));

%o f(p) = my(i=0); forprime(q=p+1, b(eulerphi(p-1))+1, i+=(eulerphi(q-1)<=eulerphi(p-1))); i;

%o forprime(p=2, 2e4, if(f(p)==0, print1(eulerphi(p-1), ", ")))

%Y Cf. A103521.

%Y Cf. also A103203, A121519.

%K nonn

%O 1,2

%A _Jianing Song_, Feb 11 2019