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 A342411 #13 Mar 11 2021 17:32:09
%S A342411 1,2,7,34,501,2600,100843,1048610,28697821,400000502,23579476911,
%T A342411 247669459528,21505924728445,340163474352620,15569560546875507,
%U A342411 576460752304472098,45798768824157052689,728637186579594211070,98646963440126439346903
%N A342411 a(n) = Sum_{k=1..n} (n/gcd(k,n))^(n/gcd(k,n) - 2).
%F A342411 a(n) = Sum_{d|n} phi(d^(d-1)) = Sum_{d|n} phi(d) * d^(d-2).
%F A342411 G.f.: Sum_{k>=1} phi(k^(k-1))*x^k/(1 - x^k).
%t A342411 a[n_] := Sum[(n/GCD[k, n])^(n/GCD[k, n] - 2), {k, 1, n}]; Array[a, 20] (* _Amiram Eldar_, Mar 11 2021 *)
%o A342411 (PARI) a(n) = sum(k=1, n, (n/gcd(k, n))^(n/gcd(k, n)-2));
%o A342411 (PARI) a(n) = sumdiv(n, d, eulerphi(d^(d-1)));
%o A342411 (PARI) a(n) = sumdiv(n, d, eulerphi(d)*d^(d-2));
%o A342411 (PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=1, N, eulerphi(k^(k-1))*x^k/(1-x^k)))
%Y A342411 Cf. A000010, A226459, A342412.
%K A342411 nonn
%O A342411 1,2
%A A342411 _Seiichi Manyama_, Mar 11 2021