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A073599 Numbers k such that the denominator of Sum_{j=1..k} 1/phi(j) divides the denominator of H(k) = Sum_{j=1..k} 1/j, the k-th harmonic number. 0
1, 2, 3, 4, 5, 6, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 27, 28, 29, 30, 31, 32, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 72, 73, 74, 75, 76, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..66.

FORMULA

It seems that for n large enough, (1/2)*n*log(n) < a(n) < n*log(n).

MATHEMATICA

Select[Range[137], Divisible @@ Denominator[Sum[{1/k, 1/EulerPhi[k]}, {k, #}]] &] (* Jayanta Basu, Jul 02 2013 *)

CROSSREFS

Sequence in context: A103681 A319824 A039265 * A039204 A039153 A272574

Adjacent sequences:  A073596 A073597 A073598 * A073600 A073601 A073602

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Aug 29 2002

STATUS

approved

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Last modified March 4 02:39 EST 2021. Contains 341774 sequences. (Running on oeis4.)