A068578 Numbers k such that tau(k)*sigma(k) > k*phi(k).

2, 3, 4, 6, 8, 10, 12, 14, 16, 18, 20, 24, 30, 36, 40, 42, 48, 60, 72, 84, 90, 120, 180

Offset: 1

Author

Benoit Cloitre, Mar 26 2002

Keywords

• nonn
• easy
• fini
• full

Comments

Numbers k such that A064840(k) > A002618(k).

Crossrefs

Cf. A000005, A000010, A000203, A002618, A064840.

Programs

Mathematica

Select[Range[180], DivisorSigma[0, #] * DivisorSigma[1, #] > # * EulerPhi[#] &] (* Amiram Eldar, Jun 12 2022 *)

PARI

is(k) = {my(f=factor(k)); numdiv(k)*sigma(k) > k*eulerphi(k); } \\ Jinyuan Wang, Apr 05 2020