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A013956 sigma_8(n), the sum of the 8th powers of the divisors of n. 7
1, 257, 6562, 65793, 390626, 1686434, 5764802, 16843009, 43053283, 100390882, 214358882, 431733666, 815730722, 1481554114, 2563287812, 4311810305, 6975757442, 11064693731, 16983563042, 25700456418 (list; graph; refs; listen; history; text; internal format)
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

FORMULA

G.f. sum(k>=1, k^8*x^k/(1-x^k)). - Benoit Cloitre, Apr 21 2003

MATHEMATICA

lst={}; Do[AppendTo[lst, DivisorSigma[8, n]], {n, 5!}]; lst (* Vladimir Joseph Stephan Orlovsky, Mar 11 2009 *)

PROG

(Sage) [sigma(n, 8)for n in xrange(1, 21)] # Zerinvary Lajos, Jun 04 2009

(PARI) a(n)=sigma(n, 8) \\ Charles R Greathouse IV, Apr 28, 2011

(MAGMA) [DivisorSigma(8, n): n in [1..30]]; // Bruno Berselli, Apr 10 2013

CROSSREFS

Sequence in context: A155468 A034682 A017679 * A036086 A000542 A023877

Adjacent sequences:  A013953 A013954 A013955 * A013957 A013958 A013959

KEYWORD

nonn,mult,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified November 22 20:13 EST 2014. Contains 249827 sequences.