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A179117 a(n) = Sum_{d|n} phi(d^phi(d)). 1
1, 2, 7, 10, 501, 20, 100843, 2058, 354301, 4502, 23579476911, 6940, 21505924728445, 3327788, 1366875507, 2147485706, 45798768824157052689, 11691722, 98646963440126439346903, 10240004510, 4203330006607501 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

LINKS

Table of n, a(n) for n=1..21.

FORMULA

Equals one-half the logarithmic derivative of A179116.

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

PROG

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

CROSSREFS

Cf. A179116, A000010 (phi).

Sequence in context: A151346 A247166 A110739 * A133154 A100020 A241807

Adjacent sequences:  A179114 A179115 A179116 * A179118 A179119 A179120

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jul 10 2010

STATUS

approved

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Last modified October 26 14:28 EDT 2021. Contains 348267 sequences. (Running on oeis4.)