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a(n) = Sum_{d|n} phi(d^phi(d)).
1

%I #6 May 09 2021 08:09:25

%S 1,2,7,10,501,20,100843,2058,354301,4502,23579476911,6940,

%T 21505924728445,3327788,1366875507,2147485706,45798768824157052689,

%U 11691722,98646963440126439346903,10240004510,4203330006607501

%N a(n) = Sum_{d|n} phi(d^phi(d)).

%C phi(n) = A000010(n) is the Euler totient function of n.

%F Equals one-half the logarithmic derivative of A179116.

%F a(n) = Sum_{k=1..n} phi(gcd(n,k)^phi(gcd(n,k)))/phi(n/gcd(n,k)). - _Richard L. Ollerton_, May 09 2021

%o (PARI) {a(n)=sumdiv(n,d,eulerphi(d^eulerphi(d)))}

%Y Cf. A179116, A000010 (phi).

%K nonn

%O 1,2

%A _Paul D. Hanna_, Jul 10 2010