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

3, 36, 504, 720, 1404, 19656, 28080, 44640, 181440, 195840, 1740960, 7637760, 46085760, 65862720, 105960960, 12884705280, 16729130880, 22826833920, 38463828480, 502503505920, 890246522880, 3377622411509760, 131727274048880640, 55340232208243752960, 2158269056121506365440

Offset

1,1

Comments

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

Links

Table of n, a(n) for n=1..25.

Tomohiro Yamada, An analog of perfect numbers involving the unitary totient function, arXiv:1806.00647 [math.NT], 2018.

Example

uphi(3) = 2 so uphi(3)/3 = 2/3;
uphi(36) = 24 so uphi(36)/36 = 2/3.

Prog

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

Crossrefs

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

Sequence in context: A199258 A262465 A322491 * A233196 A368048 A245114

Adjacent sequences: A305675 A305676 A305677 * A305679 A305680 A305681

Keyword

nonn

Author

Michel Marcus, Jun 08 2018

Status

approved