A049197 Squarefree numbers whose Euler totient function is not squarefree.

5, 10, 13, 15, 17, 19, 21, 26, 29, 30, 33, 34, 35, 37, 38, 39, 41, 42, 51, 53, 55, 57, 58, 61, 65, 66, 69, 70, 73, 74, 77, 78, 82, 85, 87, 89, 91, 93, 95, 97, 101, 102, 105, 106, 109, 110, 111, 113, 114, 115, 119, 122, 123, 127, 129, 130, 133, 137, 138, 141, 143

Offset

1,1

Comments

Numbers k such that abs(mu(k)) = 1 and mu(phi(k)) = 0.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

110 = 2*5*11 is squarefree but phi(110) = 40 is divisible by a square, so 110 is in the sequence.

Mathematica

Select[Range[144], SquareFreeQ[#] && !SquareFreeQ[EulerPhi[#]] &] (* Amiram Eldar, Feb 12 2021 *)

Prog

(PARI) isok(k) = issquarefree(k) && !issquarefree(eulerphi(k)); \\ Michel Marcus, Feb 12 2021

Crossrefs

Cf. A000010, A005117, A013929, A049195, A049196.

Sequence in context: A313378 A226386 A200995 * A324928 A009000 A198389

Adjacent sequences: A049194 A049195 A049196 * A049198 A049199 A049200

Keyword

nonn

Author

Labos Elemer

Status

approved