login
A067706
Numbers k such that phi(sigma(k)) = 3*phi(k).
2
4, 12, 30, 50, 60, 90, 120, 150, 180, 200, 225, 360, 390, 444, 528, 600, 672, 700, 714, 732, 876, 1110, 1170, 1332, 1428, 1560, 1584, 1830, 1884, 1920, 1950, 2016, 2142, 2190, 2196, 2220, 2316, 2628, 2856, 3200, 3324, 3330, 3660, 3756, 4284, 4320, 4380
OFFSET
1,1
LINKS
MATHEMATICA
Select[Range[4500], EulerPhi[DivisorSigma[1, #]] == 3*EulerPhi[#] &] (* Amiram Eldar, Apr 23 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 05 2002
STATUS
approved