A358043 Numbers k such that phi(k) is a multiple of 8.

15, 16, 17, 20, 24, 30, 32, 34, 35, 39, 40, 41, 45, 48, 51, 52, 55, 56, 60, 64, 65, 68, 70, 72, 73, 75, 78, 80, 82, 84, 85, 87, 88, 89, 90, 91, 95, 96, 97, 100, 102, 104, 105, 110, 111, 112, 113, 115, 116, 117, 119, 120, 123, 128, 130, 132, 135, 136, 137, 140, 143

Offset: 1

Author

Darío Clavijo, Oct 26 2022

Keywords

• nonn

Crossrefs

Cf. A000010 (phi), A053574 (its 2-adic valuation), A037074 (a subsequence).

Totient multiples: A066498 (3), A172019 (4), A066500 (5), A066502 (7), A332512 (12).

Programs

Mathematica

Select[Range[150], Divisible[EulerPhi[#], 8] &] (* Amiram Eldar, Oct 27 2022 *)

PARI

isok(k) = Mod(eulerphi(k), 8) == 0; \\ Michel Marcus, Oct 27 2022

Python

from sympy.ntheory import totient
def isok(n): return totient(n) % 8 == 0

Formula

A000010(a(n)) == 0 (mod 8).