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A034663 Sum of n-th powers of divisors of 21. 2
4, 32, 500, 9632, 196964, 4101152, 85884500, 1801914272, 37828630724, 794320419872, 16680163512500, 350279478046112, 7355841353205284, 154472474629724192, 3243920610749364500, 68122323330527541152 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

T. D. Noe, Table of n, a(n) for n=0..200

Index entries for linear recurrences with constant coefficients, signature (32,-262,672,-441).

FORMULA

a(n) = (1+3^n)*(1+7^n). - Bruno Berselli, Apr 17 2014

G.f.: -4*(168*x^3-131*x^2+24*x-1) / ((x-1)*(3*x-1)*(7*x-1)*(21*x-1)). - Colin Barker, May 03 2014

MATHEMATICA

Total[#^Range[0, 20]&/@Divisors[21]] (* Vincenzo Librandi, Apr 17 2014 *)

Table[(1 + 3^n) (1 + 7^n), {n, 0, 20}] (* Bruno Berselli, Apr 17 2014 *)

PROG

(Sage) [sigma(21, n)for n in xrange(0, 16)] # Zerinvary Lajos, Jun 04 2009

(MAGMA) [DivisorSigma(n, 21): n in [0..15]]; // Vincenzo Librandi, Apr 17 2014

(PARI) s=[]; for(n=0, 30, s=concat(s, sigma(21, n))); s \\ Colin Barker, May 03 2014

CROSSREFS

Sequence in context: A089285 A209197 A086906 * A192501 A192487 A093581

Adjacent sequences:  A034660 A034661 A034662 * A034664 A034665 A034666

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified November 19 22:34 EST 2019. Contains 329323 sequences. (Running on oeis4.)