%N Numbers n such that the denominator of sum(k=1,n,1/gcd(n,k)) is not equal to n.
%C Does lim n -> infinity a(n)/n = 3 ?
%e sum(k=1,6,1/gcd(6,k))=7/2 hence 6 is in the sequence but sum(k=1,12,1/gcd(12,k))=77/12 so 12 is not in the sequence.
%o (PARI) for(n=1,300,if(denominator(sum(i=1,n,1/gcd(n,i)))<n,print1(n,",")))
%A _Benoit Cloitre_, May 18 2002