A017689 - OEIS

A017689

Numerator of sum of -13th powers of divisors of n.

1, 8193, 1594324, 67117057, 1220703126, 1088524711, 96889010408, 549822930945, 2541867422653, 5000610355659, 34522712143932, 26751583696117, 302875106592254, 99226457784093, 648732096885608, 4504149450301441, 9904578032905938, 6941839931265343, 42052983462257060

(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. - Ahmed Fares (ahmedfares(AT)my-deja.com), Apr 05 2001

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000

FORMULA

From Amiram Eldar, Apr 02 2024: (Start)

sup_{n>=1} a(n)/A017690(n) = zeta(13) (A013671).

Dirichlet g.f. of a(n)/A017690(n): zeta(s)*zeta(s+13).

Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k)/A017690(k) = zeta(14) (A013672). (End)

MAPLE

A017689 := proc(n)

numtheory[sigma][-13](n) ;

numer(%) ;

end proc: # R. J. Mathar, Sep 21 2017

MATHEMATICA

Table[Numerator[DivisorSigma[13, n]/n^13], {n, 1, 20}] (* G. C. Greubel, Nov 06 2018 *)

PROG

(PARI) vector(20, n, numerator(sigma(n, 13)/n^13)) \\ G. C. Greubel, Nov 06 2018

(Magma) [Numerator(DivisorSigma(13, n)/n^13): n in [1..20]]; // G. C. Greubel, Nov 06 2018

CROSSREFS

Cf. A017690 (denominator), A013671, A013672.

Sequence in context: A300567 A323544 A230190 * A013961 A036091 A181134

Adjacent sequences: A017686 A017687 A017688 * A017690 A017691 A017692

KEYWORD

nonn,frac

AUTHOR

N. J. A. Sloane

STATUS

approved