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A090779
Numbers k that divide phi(k)^2.
2
1, 4, 8, 9, 16, 18, 25, 27, 32, 36, 49, 50, 54, 64, 72, 81, 98, 100, 108, 121, 125, 128, 144, 147, 162, 169, 196, 200, 216, 225, 242, 243, 250, 256, 288, 289, 294, 324, 338, 343, 361, 392, 400, 432, 441, 450, 484, 486, 500, 507, 512, 529, 576, 578, 588, 605, 625
OFFSET
1,2
COMMENTS
Coincides with A073539 in the first 850000 terms and possibly more. - R. J. Mathar, Sep 08 2008
FORMULA
a(n) seems to be asymptotic to c*n^2 with c = 0.1....
MATHEMATICA
Select[Range[1000], Divisible[EulerPhi[#]^2, #]&] (* Vaclav Kotesovec, Feb 16 2019 *)
CROSSREFS
Sequence in context: A070003 A325661 A073539 * A166402 A255586 A034038
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 08 2004
STATUS
approved