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A072209 Number of primitive roots of those integers with at least one primitive root. 2
1, 1, 1, 1, 2, 1, 2, 2, 2, 4, 4, 2, 8, 2, 6, 4, 10, 8, 4, 6, 12, 8, 8, 12, 6, 16, 12, 10, 22, 12, 8, 24, 6, 12, 28, 16, 8, 20, 24, 24, 12, 24, 18, 16, 40, 12, 40 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Essentially sequence A046144 with all zero entries deleted.

LINKS

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

FORMULA

a(n)=phi[phi{A033948(n)}].

MATHEMATICA

Reap[ Do[ If[n == 1, Sow[1], If[ IntegerQ[ PrimitiveRoot[n]], Sow[ EulerPhi[ EulerPhi[n]]]]] , {n, 1, 100}]][[2, 1]] (* Jean-Fran├žois Alcover, Feb 24 2012 *)

CROSSREFS

Cf. A046144.

Sequence in context: A208216 A208217 A009213 * A226559 A060169 A117958

Adjacent sequences:  A072206 A072207 A072208 * A072210 A072211 A072212

KEYWORD

nice,nonn

AUTHOR

Lekraj Beedassy, Jul 03 2002

STATUS

approved

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Last modified December 21 19:31 EST 2014. Contains 252325 sequences.