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A219028 Number of non-primitive roots for prime(n), less than prime(n). 1
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, 60, 70, 54, 72, 64, 90, 82, 72, 94, 76, 110, 108, 108, 84, 88, 90, 132, 118, 128, 112, 138, 162, 150, 114, 156, 120, 142, 176, 150, 128, 132, 136, 198, 188, 184, 190 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

FORMULA

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

a(n) = p - 1 - A008330(n) = p - 1 - A010554(p), where p is the n-th prime. - V. Raman, Nov 22 2012

MATHEMATICA

Table[c=Prime[n]; c-1-EulerPhi[EulerPhi[c]], {n, 70}] (* Harvey P. Dale, Feb 12 2013 *)

PROG

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

CROSSREFS

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

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

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

Sequence in context: A060659 A244363 A063199 * A333557 A062355 A087671

Adjacent sequences:  A219025 A219026 A219027 * A219029 A219030 A219031

KEYWORD

nonn

AUTHOR

V. Raman, Nov 10 2012

STATUS

approved

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Last modified July 13 08:26 EDT 2020. Contains 335685 sequences. (Running on oeis4.)