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 A219028 Number of non-primitive roots for prime(n), less than prime(n). 1

%I

%S 0,1,2,4,6,8,8,12,12,16,22,24,24,30,24,28,30,44,46,46,48,54,42,48,64,

%T 60,70,54,72,64,90,82,72,94,76,110,108,108,84,88,90,132,118,128,112,

%U 138,162,150,114,156,120,142,176,150,128,132,136,198,188,184,190

%N Number of non-primitive roots for prime(n), less than prime(n).

%H Harvey P. Dale, <a href="/A219028/b219028.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = p - 1 - phi(phi(p)), where p is the n-th prime.

%F a(n) = p - 1 - A008330(n) = p - 1 - A010554(p), where p is the n-th prime. - _V. Raman_, Nov 22 2012

%t Table[c=Prime[n];c-1-EulerPhi[EulerPhi[c]],{n,70}] (* _Harvey P. Dale_, Feb 12 2013 *)

%o (PARI) forprime(i=2,600,p=0;for(q=1,i-1,if(znorder(Mod(q,i))!=eulerphi(i),p++));print1(p","))

%Y Cf. A008330 (number of primitive roots for the n-th prime, less than n-th prime).

%Y Cf. A046144 (number of primitive roots for n, less than n).

%Y Cf. A010554 (value of phi(phi(n))).

%K nonn

%O 1,3

%A _V. Raman_, Nov 10 2012

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Last modified August 4 16:34 EDT 2020. Contains 336202 sequences. (Running on oeis4.)