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A017670 Denominator of sum of -3 th powers of divisors of n. 2
1, 8, 27, 64, 125, 6, 343, 512, 729, 500, 1331, 432, 2197, 343, 375, 4096, 4913, 648, 6859, 4000, 1323, 2662, 12167, 384, 15625, 8788, 19683, 2744, 24389, 125, 29791, 32768, 3993, 19652, 6125, 46656, 50653, 13718, 59319, 6400, 68921, 147, 79507, 21296, 10125 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Sum_{d|n} 1/d^k is equal to sigma_k(n)/n^k. So sequences A017665-A017712 also give the numerators and denominators of sigma_k(n)/n^k for k = 1..24. The power sums sigma_k(n) are in sequences A000203 (k=1), A001157-A001160 (k=2,3,4,5), A013954-A013972 for k = 6,7,...,24. - comment from Ahmed Fares (ahmedfares(AT)my-deja.com), Apr 05 2001.

LINKS

Table of n, a(n) for n=1..45.

FORMULA

Denominator of Sum_{d|n} 1/d^3.

MATHEMATICA

A017670[n_Integer] := Denominator[DivisorSigma[-3, n]]; A017670 /@ Range[100] (* Vladimir Joseph Stephan Orlovsky, Jul 21 2011 *)

CROSSREFS

Cf. A017669.

Sequence in context: A211641 A062686 A093322 * A126200 A213491 A076989

Adjacent sequences:  A017667 A017668 A017669 * A017671 A017672 A017673

KEYWORD

nonn,frac

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified November 28 16:31 EST 2014. Contains 250364 sequences.