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Numbers that are not squarefree whose Euler totient function is squarefree.
4

%I #17 Dec 26 2024 21:44:15

%S 4,9,18,49,98,121,242,529,961,1058,1849,1922,2209,3481,3698,4418,4489,

%T 5041,6241,6889,6962,8978,10082,10609,11449,12482,13778,17161,19321,

%U 21218,22898,27889,32041,34322,36481,38642,44521,49729,51529,55778

%N Numbers that are not squarefree whose Euler totient function is squarefree.

%H Donovan Johnson, <a href="/A049198/b049198.txt">Table of n, a(n) for n = 1..5000</a>

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

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

%o (PARI) isok(k)=!issquarefree(k) && issquarefree(eulerphi(k)) \\ _Donovan Johnson_, Jun 20 2012

%Y Intersection of A049149 and A013929.

%Y Cf. A000010, A005117, A049199.

%K nonn,easy

%O 1,1

%A _Labos Elemer_