OFFSET
1,1
COMMENTS
Chowla's function (A048050) = sum of divisors of n except 1 and n.
MATHEMATICA
okcfQ[n_]:=!Divisible[DivisorSigma[1, n]-n-1, EulerPhi[n]]
Select[Range[100], okcfQ] (* Harvey P. Dale, Feb 25 2011 *)
PROG
(PARI) j=[]; for(n=1, 400, if(Mod(sigma(n)-n-1, eulerphi(n))!=0, j=concat(j, n))); j
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, Jul 24 2001
STATUS
approved