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A319481 Integers k such that uphi(k) divides k, where uphi is the unitary phi function (A047994). 3
1, 2, 6, 12, 168, 240, 14880, 65280, 4294901760, 7608944640, 1125874137169920, 18446744069414584320 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..12.

Tomohiro Yamada, An analog of perfect numbers involving the unitary totient function, arXiv:1806.00647 [math.NT], 2018. See (2) on p. 2.

PROG

(PARI) uphi(n) = my(f=factor(n)~); prod(i=1, #f, f[1, i]^f[2, i]-1);

isok(n) = frac(n/uphi(n)) == 0;

CROSSREFS

Cf. A047994.

A030163 is a subsequence.

Sequence in context: A325504 A193619 A290406 * A195338 A179201 A105122

Adjacent sequences:  A319478 A319479 A319480 * A319482 A319483 A319484

KEYWORD

nonn,more

AUTHOR

Michel Marcus, Sep 20 2018

STATUS

approved

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Last modified July 23 12:19 EDT 2021. Contains 346259 sequences. (Running on oeis4.)