A049198 - OEIS

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A049198

Squarefull numbers whose Euler totient function is squarefree.

4, 9, 18, 49, 98, 121, 242, 529, 961, 1058, 1849, 1922, 2209, 3481, 3698, 4418, 4489, 5041, 6241, 6889, 6962, 8978, 10082, 10609, 11449, 12482, 13778, 17161, 19321, 21218, 22898, 27889, 32041, 34322, 36481, 38642, 44521, 49729, 51529, 55778

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..5000

EXAMPLE

a(27) = 13778 = 2*83*83 is divisible by a square, but phi(13778) = 6806 = 2*41*83 is squarefree.

MATHEMATICA

Abs[ MoebiusMu[ EulerPhi[ x ] ] ]=1 and Abs[ MoebiusMu[ x ] ]=0

PROG

(PARI) for(n=4, 10^7, if(issquarefree(n)==0 & issquarefree(eulerphi(n)), print1(n ", "))) /* Donovan Johnson, Jun 20 2012 */

CROSSREFS