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 A342435 #11 Mar 12 2021 09:11:58
%S A342435 1,2,5,19,129,1303,16813,262166,4782981,100000133,2357947701,
%T A342435 61917365564,1792160394049,56693912392115,1946195068359645,
%U A342435 72057594038190124,2862423051509815809,121439531096599037355
%N A342435 a(n) = Sum_{k=1..n} gcd(k,n)^(gcd(k,n) - 2).
%F A342435 a(n) = Sum_{d|n} phi(n/d) * d^(d-2).
%t A342435 a[n_] := Sum[GCD[k, n]^(GCD[k, n] - 2), {k, 1, n}]; Array[a, 20] (* _Amiram Eldar_, Mar 12 2021 *)
%o A342435 (PARI) a(n) = sum(k=1, n, gcd(k, n)^(gcd(k, n)-2));
%o A342435 (PARI) a(n) = sumdiv(n, d, eulerphi(n/d)*d^(d-2));
%Y A342435 Cf. A000010, A342423, A342436.
%K A342435 nonn
%O A342435 1,2
%A A342435 _Seiichi Manyama_, Mar 12 2021