A069167 Numbers k such that k*Sum_{d|k} 1/phi(d) is an integer.

1, 2, 4, 6, 8, 9, 10, 12, 16, 18, 24, 32, 36, 42, 44, 48, 50, 54, 64, 72, 81, 90, 96, 100, 108, 114, 126, 128, 144, 150, 162, 184, 192, 198, 200, 216, 234, 250, 252, 256, 288, 294, 324, 378, 384, 396, 400, 432, 441, 450, 484, 486, 504, 512, 550, 558, 576, 588

Offset: 1

Author

Benoit Cloitre, Apr 09 2002

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010.

Programs

Mathematica

Select[Range[600],IntegerQ[#(Total[1/(EulerPhi[Divisors[#]])])]&](* Harvey P. Dale, Dec 17 2018 *)

PARI

is(n)=denominator(sumdiv(n,d,1/eulerphi(d))*n)==1 \\ Charles R Greathouse IV, Oct 27 2015