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 A160972 a(n) = Sum_{d|n} Moebius(n/d)*d^(b-1)/phi(n) for b = 13. 3
 1, 4095, 265720, 8386560, 61035156, 1088123400, 2306881200, 17175674880, 47071500840, 249938963820, 313842837672, 2228476723200, 1941507093540, 9446678514000, 16218261652320, 35175782154240, 36413889826860 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) is the number of lattices L in Z^12 such that the quotient group Z^12 / L is C_n. - Álvar Ibeas, Nov 26 2015 REFERENCES J. H. Kwak and J. Lee, Enumeration of graph coverings, surface branched coverings and related group theory, in Combinatorial and Computational Mathematics (Pohang, 2000), ed. S. Hong et al., World Scientific, Singapore 2001, pp. 97-161. See p. 134. LINKS Álvar Ibeas, Table of n, a(n) for n = 1..10000 FORMULA a(n) = J_12(n)/J_1(n) where J_12 and J_1(n) = A000010(n) are Jordan functions. - R. J. Mathar, Jul 12 2011 From Álvar Ibeas, Nov 26 2015: (Start) Multiplicative with a(p^e) = p^(11e-11) * (p^12-1) / (p-1). For squarefree n, a(n) = A000203(n^11). (End) MATHEMATICA b = 13; Table[Sum[MoebiusMu[n/d] d^(b - 1)/EulerPhi@ n, {d, Divisors@ n}], {n, 17}] (* Michael De Vlieger, Nov 27 2015 *) PROG (PARI) vector(100, n, sumdiv(n^11, d, if(ispower(d, 12), moebius(sqrtnint(d, 12))*sigma(n^11/d), 0))) \\ Altug Alkan, Nov 26 2015 CROSSREFS Sequence in context: A075957 A075953 A011562 * A038999 A022528 A024010 Adjacent sequences:  A160969 A160970 A160971 * A160973 A160974 A160975 KEYWORD nonn,mult AUTHOR N. J. A. Sloane, Nov 19 2009 EXTENSIONS Definition corrected by Enrique Pérez Herrero, Oct 30 2010 STATUS approved

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