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A074701 Numbers n such that n = sum( d dividing phi(n), mu(phi(d))*phi(n)/d ). 2
1, 3, 5, 25, 125, 625, 3125, 15625, 78125, 390625, 1953125, 9765625, 48828125, 244140625, 1220703125, 6103515625, 30517578125, 152587890625, 762939453125, 3814697265625, 19073486328125, 95367431640625, 476837158203125, 2384185791015625, 11920928955078125, 59604644775390625, 298023223876953125 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Does sequence consist of 1,3 and all powers of 5? Answer from Lambert Klasen, Oct 07 2005: Yes! See attached file.

LINKS

Table of n, a(n) for n=1..27.

Lambert Klasen, Notes on A074701

MAPLE

with(numtheory): a:=proc(n) local div: div:=convert(divisors(phi(n)), list): if add(mobius(phi(div[j]))*phi(n)/div[j], j=1..nops(div))=n then n else fi end: seq(a(n), n=1..5000); # Emeric Deutsch, Mar 27 2005

PROG

(PARI) isok(n) = n == sumdiv(eulerphi(n), d, moebius(eulerphi(d))*eulerphi(n)/d); \\ Michel Marcus, Aug 15 2019

CROSSREFS

Cf. A000351. [R. J. Mathar, Sep 23 2008]

Sequence in context: A009002 A119882 A276968 * A318179 A327468 A140127

Adjacent sequences:  A074698 A074699 A074700 * A074702 A074703 A074704

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Sep 03 2002

EXTENSIONS

2 more terms from Emeric Deutsch, Mar 27 2005

STATUS

approved

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Last modified October 21 11:42 EDT 2019. Contains 328296 sequences. (Running on oeis4.)