A062973 Chowla function of n is not divisible by phi(n).

6, 8, 9, 10, 12, 14, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98

Offset: 1

Author

Jason Earls, Jul 24 2001

Keywords

• nonn

Comments

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

Programs

Mathematica

okcfQ[n_]:=!Divisible[DivisorSigma[1,n]-n-1,EulerPhi[n]]
Select[Range[100],okcfQ]  (* Harvey P. Dale, Feb 25 2011 *)

PARI

j=[]; for(n=1,400, if(Mod(sigma(n)-n-1,eulerphi(n))!=0,j=concat(j,n))); j