A306371 Number of primitive roots of prime A103521(n).

1, 2, 4, 6, 8, 12, 16, 20, 24, 32, 36, 40, 48, 64, 72, 80, 96, 120, 144, 160, 176, 200, 216, 240, 288, 320, 336, 384, 432, 448, 480, 576, 720, 768, 880, 960, 1056, 1200, 1280, 1344, 1440, 1664, 1680, 1728, 1920, 2112, 2208, 2304, 2400, 2592, 2784, 2880, 3072, 3456, 3840, 4224, 4320

Offset: 1

Author

Jianing Song, Feb 11 2019

Keywords

• nonn

Comments

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

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

Crossrefs

Cf. A103521.

Cf. also A103203, A121519.

Programs

PARI

b(n) = if(n==1, 2, floor(exp(Euler)*n*log(log(n^2))+2.5*n/log(log(n^2))));
f(p) = my(i=0); forprime(q=p+1, b(eulerphi(p-1))+1, i+=(eulerphi(q-1)<=eulerphi(p-1))); i;
forprime(p=2, 2e4, if(f(p)==0, print1(eulerphi(p-1), ", ")))

Formula

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