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 A070999 Numbers n such that the denominator of sum(k=1,n,1/gcd(n,k)) is not equal to n. 0

%I

%S 6,15,18,21,30,33,35,42,44,45,48,51,54,60,66,69,70,78,84,87,90,99,102,

%T 105,114,119,120,123,126,132,133,135,138,140,141,144,147,150,153,159,

%U 162,165,168,174,177,180,186,195,198,204,207,210,213,217,220,221,222

%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,",")))

%K easy,nonn

%O 1,1

%A _Benoit Cloitre_, May 18 2002

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Last modified October 14 18:28 EDT 2019. Contains 328022 sequences. (Running on oeis4.)