|
| |
|
|
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] (* From 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
|
| |
|
|
