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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
 6, 15, 18, 21, 30, 33, 35, 42, 44, 45, 48, 51, 54, 60, 66, 69, 70, 78, 84, 87, 90, 99, 102, 105, 114, 119, 120, 123, 126, 132, 133, 135, 138, 140, 141, 144, 147, 150, 153, 159, 162, 165, 168, 174, 177, 180, 186, 195, 198, 204, 207, 210, 213, 217, 220, 221, 222 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Does lim n -> infinity a(n)/n = 3 ? LINKS EXAMPLE 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. PROG (PARI) for(n=1, 300, if(denominator(sum(i=1, n, 1/gcd(n, i)))

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Last modified July 21 19:25 EDT 2019. Contains 325199 sequences. (Running on oeis4.)