OFFSET
1,1
EXAMPLE
For n = 32 holds: 1/1 + 1/2 + 2/4 + 4/8 + 8/16 = 3 (integer).
MATHEMATICA
t = {}; Do[d2 = Sum[EulerPhi[d]/d, {d, Most[Divisors[n]]}]; If[IntegerQ[d2], AppendTo[t, n]], {n, 2, 233}]; t (* T. D. Noe, Apr 26 2012 *)
PROG
(PARI) is(n)=denominator(sumdiv(n, d, if(d<n, eulerphi(d)/d)))==1 \\ Charles R Greathouse IV, Feb 21 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Apr 20 2012
STATUS
approved