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A017667
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Numerator of sum of -2 th powers of divisors of n.
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2
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1, 5, 10, 21, 26, 25, 50, 85, 91, 13, 122, 35, 170, 125, 52, 341, 290, 455, 362, 273, 500, 305, 530, 425, 651, 425, 820, 75, 842, 13, 962, 1365, 1220, 725, 52, 637, 1370, 905, 1700, 221, 1682, 625, 1850, 1281, 2366, 1325, 2210, 1705, 2451, 651, 2900, 1785
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OFFSET
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1,2
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COMMENTS
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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.
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LINKS
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Table of n, a(n) for n=1..52.
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FORMULA
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Dirichlet generating function: zeta(s)*zeta(s+2) [for fraction A017667/A017668]. - Franklin T. Adams-Watters, Sep 11 2005.
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MATHEMATICA
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A017667[n_Integer] := Numerator[DivisorSigma[-2, n]]; A017667 /@ Range[100] (* From Vladimir Joseph Stephan Orlovsky, Jul 21 2011 *)
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CROSSREFS
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Cf. A017668.
Sequence in context: A106367 A002791 A080399 * A001157 A002800 A132174
Adjacent sequences: A017664 A017665 A017666 * A017668 A017669 A017670
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KEYWORD
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nonn,frac
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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