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A059247 Denominator of Sum_{j=1..n} d(j)/n, where d = number of divisors function (A000005). 3
1, 2, 3, 1, 1, 3, 7, 2, 9, 10, 11, 12, 13, 14, 1, 8, 17, 9, 19, 10, 3, 11, 23, 2, 25, 2, 27, 28, 29, 10, 31, 32, 11, 34, 35, 9, 37, 19, 13, 20, 41, 1, 43, 1, 45, 23, 1, 8, 49, 50, 51, 52, 53, 54, 5, 56, 19, 58, 59, 20, 61, 62, 3, 8, 65, 33, 67, 17, 69, 35, 71 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

M. Aigner and G. M. Ziegler, Proofs from The Book, Springer-Verlag, Berlin, 1999; see p. 135.

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = denominator(A006218(n)/n). - Michel Marcus, Jan 03 2017

EXAMPLE

1, 3/2, 5/3, 2, 2, 7/3, 16/7, 5/2, 23/9, 27/10, ...

MATHEMATICA

Denominator[Table[Sum[DivisorSigma[0, j]/n, {j, 1, n}], {n, 1, 100}]] (* G. C. Greubel, Jan 02 2016 *)

PROG

(PARI) a(n) = denominator(sum(j=1, n, numdiv(j))/n); \\ Michel Marcus, Jan 03 2017

CROSSREFS

Cf. A006218, A059246 and also A059248/A035105.

Sequence in context: A135392 A071947 A139343 * A244665 A194518 A023572

Adjacent sequences:  A059244 A059245 A059246 * A059248 A059249 A059250

KEYWORD

nonn,frac

AUTHOR

N. J. A. Sloane, Jan 21 2001

STATUS

approved

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Last modified August 22 20:39 EDT 2019. Contains 326188 sequences. (Running on oeis4.)