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

1,1

Comments

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

Links

Table of n, a(n) for n=1..23.

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A055721 A064376 A283808 * A203812 A047894 A113769

Adjacent sequences: A068575 A068576 A068577 * A068579 A068580 A068581

Keyword

nonn,easy,fini,full

Author

Benoit Cloitre, Mar 26 2002

Status

approved