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 A160894 #14 Nov 09 2022 07:56:45 %S A160894 31,465,1240,3720,4836,18600,12400,29760,33480,72540,45384,148800, %T A160894 73780,186000,193440,238080,161820,502200,224440,580320,496000,680760, %U A160894 394320,1190400,604500,1106700,903960,1488000,783060,2901600,954304,1904640,1815360,2427300 %N A160894 a(n) = ((2^b-1)/phi(n))*Sum_{d|n} Moebius(n/d)*d^(b-1) for b = 5. %H A160894 Amiram Eldar, <a href="/A160894/b160894.txt">Table of n, a(n) for n = 1..10000</a> %H A160894 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 A160894 a(n) = 31*A160891(n). - _R. J. Mathar_, Mar 16 2016 %F A160894 From _Amiram Eldar_, Nov 08 2022: (Start) %F A160894 Sum_{k=1..n} a(k) ~ c * n^4, where c = (31/4) * Product_{p prime} (1 + 1/p^2 + 1/p^3 + 1/p^4) = 14.3522727306... . %F A160894 Sum_{k>=1} 1/a(k) = (zeta(3)*zeta(4)/31) * Product_{p prime} (1 - 2/p^4 + 1/p^7) = 0.03599754726... . (End) %t A160894 f[p_, e_] := p^(3 e - 3)*(1 + p + p^2 + p^3); a[1] = 31; a[n_] := 31 * Times @@ f @@@ FactorInteger[n]; Array[a, 32] (* _Amiram Eldar_, Nov 08 2022 *) %o A160894 (PARI) a(n) = {my(f = factor(n)); 31 * prod(i = 1, #f~, (f[i,1]^3 + f[i,1]^2 + f[i,1] + 1)*f[i,1]^(3*f[i,2] - 3));} \\ _Amiram Eldar_, Nov 08 2022 %Y A160894 Cf. A000010, A002117, A013662, A160891. %K A160894 nonn %O A160894 1,1 %A A160894 _N. J. A. Sloane_, Nov 19 2009