BBC Russian

A353683

Numbers k for which phi(sigma(k)) > phi(k).

2, 4, 6, 8, 9, 10, 12, 14, 16, 18, 20, 21, 22, 24, 25, 28, 30, 32, 34, 36, 40, 42, 44, 46, 48, 50, 52, 54, 56, 60, 62, 63, 64, 66, 68, 70, 72, 75, 76, 78, 80, 81, 84, 88, 90, 92, 93, 94, 96, 98, 100, 102, 105, 106, 108, 110, 112, 114, 120, 124, 126, 128, 130, 132, 136, 138, 140, 142, 144, 148, 150, 152, 154, 156, 160

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Numbers k such that A062401(k) > A000010(k).

LINKS

Table of n, a(n) for n=1..75.

Index entries for sequences related to sigma(n)

MATHEMATICA

Select[Range[160], EulerPhi[DivisorSigma[1, #]] > EulerPhi[#] &] (* Amiram Eldar, May 06 2022 *)

PROG

(PARI)