A138304 - OEIS

A138304

Number of prime primitive roots of prime(n).

0, 1, 2, 2, 2, 3, 4, 3, 5, 4, 4, 5, 6, 4, 9, 6, 8, 6, 7, 9, 8, 8, 11, 12, 11, 12, 7, 12, 9, 16, 11, 11, 17, 9, 18, 6, 11, 17, 23, 18, 20, 13, 20, 16, 19, 13, 12, 15, 24, 20, 28, 24, 17, 23, 28, 32, 29, 15, 24, 23, 13, 31, 20, 32, 23, 28, 15, 21, 32, 22, 28, 42, 27, 29, 21, 43, 40, 27

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OFFSET

1,3

LINKS

T. D. Noe, Table of n, a(n) for n=1..10000

EXAMPLE

a(5)=2 because the primitive roots of 11 are 2, 6, 7 and 8, two of which are prime.

MATHEMATICA

Table[p=Prime[n]; g=Select[Prime[Range[n-1]], MultiplicativeOrder[ #, p]==p-1&]; Length[g], {n, 100}]

CROSSREFS

Cf. A060749 (primitive roots), A138304 (prime primitive roots).

Sequence in context: A330216 A241952 A236919 * A054860 A098745 A029158

Adjacent sequences: A138301 A138302 A138303 * A138305 A138306 A138307

KEYWORD

nonn

AUTHOR

T. D. Noe, Mar 14 2008

STATUS

approved