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A099378 Denominators of the harmonic means of the divisors of the positive integers. 7
1, 3, 2, 7, 3, 1, 4, 15, 13, 9, 6, 7, 7, 3, 2, 31, 9, 13, 10, 7, 8, 9, 12, 5, 31, 21, 10, 1, 15, 3, 16, 21, 4, 27, 12, 91, 19, 15, 14, 9, 21, 2, 22, 7, 13, 9, 24, 31, 19, 31, 6, 49, 27, 5, 18, 15, 20, 45, 30, 7, 31, 12, 52, 127, 21, 3, 34, 21, 8, 9, 36, 65, 37, 57, 62, 35, 24, 7, 40, 93 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..10000

Eric Weisstein's World of Mathematics, Ore's Conjecture

EXAMPLE

1, 4/3, 3/2, 12/7, 5/3, 2, 7/4, 32/15, ...

MATHEMATICA

f[n_] := DivisorSigma[0, n]/Plus @@ (1/Divisors@n); Denominator@ Array[f, 80] (* Robert G. Wilson v, Aug 04 2010 *)

Table[Denominator[DivisorSigma[0, n]/DivisorSigma[-1, n]], {n, 80}] (* Ivan Neretin, Nov 13 2016 *)

PROG

(PARI) a(n) = my(d=divisors(n)); denominator(#d/sum(k=1, #d, 1/d[k])); \\ Michel Marcus, Nov 13 2016

CROSSREFS

Cf. A099377.

Sequence in context: A308439 A245601 A296513 * A182885 A182891 A071190

Adjacent sequences:  A099375 A099376 A099377 * A099379 A099380 A099381

KEYWORD

nonn,frac

AUTHOR

Eric W. Weisstein, Oct 13 2004

EXTENSIONS

More terms from Robert G. Wilson v, Aug 04 2010

STATUS

approved

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Last modified April 7 13:36 EDT 2020. Contains 333305 sequences. (Running on oeis4.)