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 A161024 #10 Nov 09 2022 07:55:23
%S A161024 8191,33542145,2176512520,68694312960,499938962796,8912818769400,
%T A161024 18895663909200,140685952942080,385562663380440,2047250052649620,
%U A161024 2570686683371352,18253452839731200,15902884603186140,77377743708174000,132843781194153120,288124831625379840
%N A161024 a(n) = ((2^b-1)/phi(n))*Sum_{d|n} Moebius(n/d)*d^(b-1) for b = 13.
%H A161024 Amiram Eldar, <a href="/A161024/b161024.txt">Table of n, a(n) for n = 1..10000</a>
%H A161024 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.
%F A161024 From _Amiram Eldar_, Nov 08 2022: (Start)
%F A161024 a(n) = 8191 * A160972(n).
%F A161024 Sum_{k=1..n} a(k) ~ c * n^12, where c = (8191/12) * Product_{p prime} (1 + (p^11-1)/((p-1)*p^12)) = 1326.4495346... .
%F A161024 Sum_{k>=1} 1/a(k) = (zeta(11)*zeta(12)/8191) * Product_{p prime} (1 - 2/p^12 + 1/p^23) = 0.0001221155049... . (End)
%t A161024 f[p_, e_] := p^(11*e - 11) * (p^12-1) / (p-1); a[1] = 8191; a[n_] := 8191 * Times @@ f @@@ FactorInteger[n]; Array[a, 20] (* _Amiram Eldar_, Nov 08 2022 *)
%o A161024 (PARI) a(n) = {my(f = factor(n)); 8191 * prod(i = 1, #f~, (f[i,1]^12 - 1)*f[i,1]^(11*f[i,2] - 11)/(f[i,1] - 1));} \\ _Amiram Eldar_, Nov 08 2022
%Y A161024 Cf. A000010, A013669, A013670, A160972.
%K A161024 nonn
%O A161024 1,1
%A A161024 _N. J. A. Sloane_, Nov 19 2009