A350777 Numbers k where phi(k) divides k - 3.

1, 2, 3, 9, 195, 5187, 1141967133868035, 3658018932844533311864835

Offset

1,2

Comments

Numbers in this sequence larger than 2 have to be odd, since phi(n) is even for n > 2, so n - 3 cannot be odd. Therefore n itself must be odd.

Terms having (k-3)/phi(k) = 2 are shared with A226105. - Max Alekseyev, Oct 26 2023

Links

Table of n, a(n) for n=1..8.

Example

phi(195) = 96, 195 - 3 = 192, and 96 divides 192.

Mathematica

Select[Range[6000], Divisible[#-3, EulerPhi[#]] &] (* Amiram Eldar, Jan 19 2022 *)

Prog

(PARI) isok(k) = !((k-3) % eulerphi(k)); \\ Michel Marcus, Jan 19 2022
(Python)
from sympy import totient
print("1, 2", end=", ")
for k in range (3, 10**8, 2):
    if (k-3)%totient(k)==0:
        print(k, end=", ", flush=True) # Martin Ehrenstein, Mar 26 2022

Crossrefs

Cf. A000010, A007694, A226105.

Sequence in context: A333474 A251543 A332203 * A248236 A319157 A153702

Adjacent sequences: A350774 A350775 A350776 * A350778 A350779 A350780

Keyword

nonn,more

Author

Albert Böschow and Dennis Gruhlke, Jan 15 2022

Extensions

a(7)-a(8) from Max Alekseyev, Nov 5 2023

Status

approved