This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A160960 #36 Apr 03 2025 02:56:25
%S A160960 1,2047,88573,2096128,12207031,181308931,329554457,2146435072,
%T A160960 5230147077,24987792457,28531167061,185660345344,149346699503,
%U A160960 674597973479,1081213356763,2197949513728,2141993519227,10706111066619,6471681049901,25587499475968,29189626919861,58403298973867
%N A160960 a(n) = Sum_{d|n} Moebius(n/d)*d^(b-1)/phi(n) for b = 12.
%C A160960 a(n) is the number of lattices L in Z^11 such that the quotient group Z^11 / L is C_n. - _Álvar Ibeas_, Nov 26 2015
%H A160960 Álvar Ibeas, <a href="/A160960/b160960.txt">Table of n, a(n) for n = 1..10000</a>
%H A160960 Jin Ho Kwak and Jaeun Lee, <a href="https://doi.org/10.1142/9789812799890_0005">Enumeration of graph coverings, surface branched coverings and related group theory</a>, in Combinatorial and Computational Mathematics (Pohang, 2000), ed. S. Hong et al., World Scientific, Singapore 2001, pp. 97-161. See p. 134.
%H A160960 <a href="/index/J#nome">Index to Jordan function ratios J_k/J_1</a>.
%F A160960 a(n) = J_11(n)/J_1(n) where J_11 and J_1(n) = A000010(n) are Jordan functions. - _R. J. Mathar_, Jul 12 2011
%F A160960 From _Álvar Ibeas_, Nov 26 2015: (Start)
%F A160960 Multiplicative with a(p^e) = p^(10e-10) * (p^11-1) / (p-1).
%F A160960 For squarefree n, a(n) = A000203(n^10). (End)
%F A160960 From _Amiram Eldar_, Nov 08 2022: (Start)
%F A160960 Sum_{k=1..n} a(k) ~ c * n^11, where c = (1/11) * Product_{p prime} (1 + (p^10-1)/((p-1)*p^11)) = 0.1766326404... .
%F A160960 Sum_{k>=1} 1/a(k) = zeta(10)*zeta(11) * Product_{p prime} (1 - 2/p^11 + 1/p^21) = 1.0005003781952... . (End)
%F A160960 a(n) = (1/n) * Sum_{d|n} mu(n/d)*sigma(d^11). - _Ridouane Oudra_, Apr 02 2025
%t A160960 b = 12; Table[Sum[MoebiusMu[n/d] d^(b - 1)/EulerPhi@ n, {d, Divisors@ n}], {n, 18}] (* _Michael De Vlieger_, Nov 27 2015 *)
%t A160960 f[p_, e_] := p^(10*e - 10) * (p^11-1) / (p-1); a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 25] (* _Amiram Eldar_, Nov 08 2022 *)
%o A160960 (PARI) vector(100, n, sumdiv(n^10, d, if(ispower(d, 11), moebius(sqrtnint(d, 11))*sigma(n^10/d), 0))) \\ _Altug Alkan_, Nov 26 2015
%o A160960 (PARI) a(n) = {my(f = factor(n)); prod(i = 1, #f~, (f[i,1]^11 - 1)*f[i,1]^(10*f[i,2] - 10)/(f[i,1] - 1));} \\ _Amiram Eldar_, Nov 08 2022
%Y A160960 Column 11 of A263950.
%Y A160960 Cf. A000010, A000203, A008683, A013668, A013669.
%K A160960 nonn,mult
%O A160960 1,2
%A A160960 _N. J. A. Sloane_, Nov 19 2009
%E A160960 Definition corrected by _Enrique Pérez Herrero_, Oct 30 2010