A067706 Numbers k such that phi(sigma(k)) = 3*phi(k).

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

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

Mathematica

Select[Range[4500], EulerPhi[DivisorSigma[1, #]] == 3*EulerPhi[#] &] (* Amiram Eldar, Apr 23 2022 *)

Crossrefs

Cf. A000010, A000203, A062401, A200905.

Sequence in context: A296645 A280007 A061726 * A008261 A099407 A011938

Adjacent sequences: A067703 A067704 A067705 * A067707 A067708 A067709

Keyword

nonn

Author

Benoit Cloitre, Feb 05 2002

Status

approved