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A049199
Nonsquarefree numbers whose Euler totient function is also nonsquarefree.
3
8, 12, 16, 20, 24, 25, 27, 28, 32, 36, 40, 44, 45, 48, 50, 52, 54, 56, 60, 63, 64, 68, 72, 75, 76, 80, 81, 84, 88, 90, 92, 96, 99, 100, 104, 108, 112, 116, 117, 120, 124, 125, 126, 128, 132, 135, 136, 140, 144, 147, 148, 150, 152, 153, 156, 160, 162, 164, 168, 169
OFFSET
1,1
COMMENTS
Prime powers with sufficiently large exponents are in this sequence, including 8, 16, 32, 64, ..., 27, 81, ..., 25, 125.
LINKS
FORMULA
k such that abs(mu(k)) = 0 and abs(mu(phi(k))) = 0.
EXAMPLE
124 = 4*31 is in the sequence because phi(124)=60 and neither 124 nor 60 is squarefree.
MATHEMATICA
Select[Range[170], !SquareFreeQ[#] && !SquareFreeQ[EulerPhi[#]] &] (* Amiram Eldar, Jul 13 2019 *)
PROG
(PARI) isok(n) = !issquarefree(n) && ! issquarefree(eulerphi(n)); \\ Michel Marcus, Jul 13 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved