A362008 Numbers whose Euler's cototient is divisible by 9.

21, 27, 34, 54, 63, 68, 78, 81, 106, 108, 115, 117, 126, 129, 135, 136, 142, 147, 156, 162, 171, 178, 183, 186, 187, 189, 195, 205, 210, 212, 214, 216, 234, 237, 243, 252, 270, 272, 279, 284, 291, 295, 297, 312, 315, 324, 333, 342, 351, 356, 358, 372, 378

Offset

1,1

Comments

Numbers k such that A010888(totient(k)) = A010888(k).

Links

Table of n, a(n) for n=1..53.

Mathematica

Select[Range[2, 400], Mod[#-EulerPhi[#], 9]==0&] (* Harvey P. Dale, Jan 22 2024 *)

Prog

(Python)
from sympy import totient
def isok(n):
  return (n-totient(n)) % 9 == 0

Crossrefs

Cf. A000010, A051953, A010888.

Sequence in context: A352096 A103246 A206347 * A247316 A072392 A144415

Adjacent sequences: A362005 A362006 A362007 * A362009 A362010 A362011

Keyword

nonn,easy

Author

Darío Clavijo, Apr 03 2023

Status

approved