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 A305678 Solutions x of uphi(x)/x = 2/3, where uphi is the unitary phi function (A047994). 4

%I

%S 3,36,504,720,1404,19656,28080,44640,181440,195840,1740960,7637760,

%T 46085760,65862720,105960960,12884705280,16729130880,22826833920,

%U 38463828480,502503505920,890246522880,3377622411509760,131727274048880640,55340232208243752960,2158269056121506365440

%N Solutions x of uphi(x)/x = 2/3, where uphi is the unitary phi function (A047994).

%C Apparently, these is a single x, 6, such that uphi(x)/x = 1/3.

%H Tomohiro Yamada, <a href="https://arxiv.org/abs/1806.00647">An analog of perfect numbers involving the unitary totient function</a>, arXiv:1806.00647 [math.NT], 2018.

%e uphi(3) = 2 so uphi(3)/3 = 2/3;

%e uphi(36) = 24 so uphi(36)/36 = 2/3.

%o (PARI) solve_uphi(2, 3, 10^40) \\ see A030163

%Y Cf. A047994 (uphi), A030163 (uphi(x)/x = 1/2).

%K nonn

%O 1,1

%A _Michel Marcus_, Jun 08 2018

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Last modified May 27 13:04 EDT 2022. Contains 354097 sequences. (Running on oeis4.)