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A049196
Squarefree numbers whose Euler totient function is also squarefree.
2
1, 2, 3, 6, 7, 11, 14, 22, 23, 31, 43, 46, 47, 59, 62, 67, 71, 79, 83, 86, 94, 103, 107, 118, 131, 134, 139, 142, 158, 166, 167, 179, 191, 206, 211, 214, 223, 227, 239, 262, 263, 278, 283, 311, 331, 334, 347, 358, 359, 367, 382, 383, 419, 422, 431, 439, 443, 446
OFFSET
1,2
LINKS
FORMULA
k such that abs(mu(k)) = 1 and abs(mu(phi(k))) = 1.
EXAMPLE
86 is here because it is squarefree and the same holds for phi(86) = 42.
MATHEMATICA
Select[Range[500], And@@SquareFreeQ/@{#, EulerPhi[#]}&] (* Harvey P. Dale, Nov 05 2013 *)
PROG
(Magma) [n:n in [1..500]| IsSquarefree(n) and IsSquarefree(EulerPhi(n))]; // Marius A. Burtea, Jul 11 2019
(PARI) isok(m) = issquarefree(m) && issquarefree(eulerphi(m)); \\ Michel Marcus, Jul 12 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved