A013965 a(n) = sigma_17(n), the sum of the 17th powers of the divisors of n.

1, 131073, 129140164, 17180000257, 762939453126, 16926788715972, 232630513987208, 2251816993685505, 16677181828806733, 100000762939584198, 505447028499293772, 2218628050709022148, 8650415919381337934, 30491579359845314184, 98526126098761952664

Offset

1,2

Comments

If the canonical factorization of n into prime powers is the product of p^e(p) then sigma_k(n) = Product_p ((p^((e(p)+1)*k))-1)/(p^k-1).

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

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for sequences related to sigma(n).

Formula

G.f.: Sum_{k>=1} k^17*x^k/(1-x^k). - Benoit Cloitre, Apr 21 2003

Dirichlet g.f.: zeta(s-17)*zeta(s). - Ilya Gutkovskiy, Sep 10 2016

Empirical: Sum_{n>=1} a(n)/exp(2*Pi*n) = 43867/28728, also equals Bernoulli(18)/36. - Simon Plouffe, May 06 2023

From Amiram Eldar, Oct 29 2023: (Start)

Multiplicative with a(p^e) = (p^(17*e+17)-1)/(p^17-1).

Sum_{k=1..n} a(k) = zeta(18) * n^18 / 18 + O(n^19). (End)

Mathematica

DivisorSigma[17, Range[20]] (* Harvey P. Dale, May 30 2013 *)

Prog

(Sage) [sigma(n, 17)for n in range(1, 14)] # Zerinvary Lajos, Jun 04 2009
(Magma) [DivisorSigma(17, n): n in [1..20]]; // Vincenzo Librandi, Sep 10 2016
(PARI) my(N=99, q='q+O('q^N)); Vec(sum(n=1, N, n^17*q^n/(1-q^n))) \\ Altug Alkan, Sep 10 2016
(PARI) a(n) = sigma(n, 17); \\ Amiram Eldar, Oct 29 2023

Crossrefs

Cf. A000203, A001157-A001160, A013676, A013954-A013972, A017665-A017712.

Sequence in context: A236225 A323546 A017697 * A036095 A214290 A187939

Adjacent sequences: A013962 A013963 A013964 * A013966 A013967 A013968

Keyword

nonn,easy,mult

Author

N. J. A. Sloane

Status

approved