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 A007517 #25 Dec 04 2023 01:34:41
%S A007517 0,1,2,6,4,12,6,28,24,32,10,64,12,60,72,120,16,126,18,176,132,140,22,
%T A007517 288,120,192,234,336,28,336,30,496,300,320,312,660,36,396,408,800,40,
%U A007517 648,42,800,792,572,46,1216,336,860,672,1104,52,1188,680
%N A007517 a(n) = phi(n) * (sigma(n) - n).
%H A007517 G. C. Greubel, <a href="/A007517/b007517.txt">Table of n, a(n) for n = 1..10000</a>
%F A007517 a(n) = A000010(n)*A001065(n). - _Michel Marcus_, Mar 22 2018
%F A007517 Sum_{k=1..n} a(k) ~ c * n^2 / 3, where c = A065465 - A059956 = 0.273586... . - _Amiram Eldar_, Dec 04 2023
%p A007517 with(numtheory): seq(phi(n)*(sigma(n)-n),n=1..60); # _Muniru A Asiru_, Mar 22 2018
%t A007517 Table[EulerPhi[n](DivisorSigma[1,n]-n),{n,60}] (* _Harvey P. Dale_, Mar 16 2013 *)
%o A007517 (GAP) List([1..60],n->Phi(n)*(Sigma(n)-n)); # _Muniru A Asiru_, Mar 22 2018
%o A007517 (PARI) for(n=1,50, print1(eulerphi(n)*(sigma(n) - n), ", ")) \\ _G. C. Greubel_, Mar 22 2018
%Y A007517 Cf. A000010, A000203, A001065, A059956, A065465.
%K A007517 nonn,easy
%O A007517 1,3
%A A007517 _Walter Nissen_