login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified December 6 03:18 EST 2016. Contains 278772 sequences.