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 A342424 #13 Mar 13 2021 10:05:13 %S A342424 1,3,5,10,9,33,13,60,69,167,21,470,25,837,1245,1624,33,5067,37,9570, %T A342424 13841,20633,45,54612,12545,98511,119601,201646,57,562957,61,794928, %U A342424 1774185,2097491,536037,5381754,73,9437601,19136333,14296940 %N A342424 a(n) = Sum_{k=1..n} gcd(k,n)^(n/gcd(k,n)). %H A342424 Seiichi Manyama, <a href="/A342424/b342424.txt">Table of n, a(n) for n = 1..5000</a> %F A342424 a(n) = Sum_{d|n} phi(n/d) * d^(n/d). %t A342424 a[n_] := Sum[GCD[k, n]^(n/GCD[k, n]), {k, 1, n}]; Array[a, 40] (* _Amiram Eldar_, Mar 11 2021 *) %o A342424 (PARI) a(n) = sum(k=1, n, gcd(k, n)^(n/gcd(k, n))); %o A342424 (PARI) a(n) = sumdiv(n, d, eulerphi(n/d)*d^(n/d)); %Y A342424 Cf. A000010, A332517, A342423. %K A342424 nonn %O A342424 1,2 %A A342424 _Seiichi Manyama_, Mar 11 2021