A062972 Numbers k such that the Chowla function of k is divisible by phi(k).

1, 2, 3, 4, 5, 7, 11, 13, 15, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269

Offset: 1

Author

Jason Earls, Jul 24 2001

Keywords

• nonn

Comments

Chowla's function (A048050) = sum of divisors of n except 1 and n.

Sequence contains all primes; see A070037 for nonprime terms. - Charles R Greathouse IV, Apr 14 2010

Links

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

Crossrefs

Cf. A000010, A048050, A070037.

Programs

Mathematica

chowla[1] = 0; chowla[n_] := DivisorSigma[1, n] - n - 1; Select[Range[270], Divisible[chowla[#], EulerPhi[#]] &] (* Amiram Eldar, Dec 01 2019 *)

PARI

j=[]; for(n=1,600, if(Mod(sigma(n)-n-1,eulerphi(n)) == 0,j=concat(j,n))); j