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 A342618 #16 Mar 18 2021 08:25:10
%S A342618 1,2,129,514,4194305,9218,470184984577,17179877378,609359740018689,
%T A342618 4402341478402,100000000000000000000001,1125899907563522,
%U A342618 137370551967459378662586974209,36845784908492735250434,9903520314283046597240029185
%N A342618 a(n) = Sum_{d|n} phi(d)^(n+d+1).
%H A342618 Seiichi Manyama, <a href="/A342618/b342618.txt">Table of n, a(n) for n = 1..220</a>
%F A342618 a(n) = Sum_{k=1..n} phi(n/gcd(k,n))^(n + n/gcd(k,n)).
%F A342618 G.f.: Sum_{k>=1} phi(k)^(2*k+1) * x^k/(1 - (phi(k) * x)^k).
%F A342618 If p is prime, a(p) = 1 + (p-1)^(2*p+1).
%t A342618 a[n_] := DivisorSum[n, EulerPhi[#]^(n + # + 1) &]; Array[a, 15] (* _Amiram Eldar_, Mar 17 2021 *)
%o A342618 (PARI) a(n) = sumdiv(n, d, eulerphi(d)^(n+d+1));
%o A342618 (PARI) a(n) = sum(k=1, n, eulerphi(n/gcd(k, n))^(n+n/gcd(k, n)));
%o A342618 (PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=1, N, eulerphi(k)^(2*k+1)*x^k/(1-(eulerphi(k)*x)^k)))
%Y A342618 Cf. A000010, A342608.
%K A342618 nonn
%O A342618 1,2
%A A342618 _Seiichi Manyama_, Mar 16 2021