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 A017667 Numerator of sum of -2nd powers of divisors of n. 2
 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 (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 FORMULA Dirichlet generating function: zeta(s)*zeta(s+2) [for fraction A017667/A017668]. - Franklin T. Adams-Watters, Sep 11 2005 MATHEMATICA A017667[n_Integer] := Numerator[DivisorSigma[-2, n]]; A017667 /@ Range[100] (* Vladimir Joseph Stephan Orlovsky, Jul 21 2011 *) CROSSREFS Cf. A017668. Sequence in context: A244022 A002791 A080399 * A241603 A242643 A276959 Adjacent sequences:  A017664 A017665 A017666 * A017668 A017669 A017670 KEYWORD nonn,frac AUTHOR STATUS approved

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