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A067732 Numbers k such that phi(prime(k) + 1) == 0 (mod k). 0
1, 2, 4, 6, 8, 24, 36, 48, 80, 192, 1440, 3960, 5184, 5478, 6480, 16080, 20336, 29628, 40073, 40083, 43056, 44980, 85800, 200320, 241920, 252378, 258048, 287040, 697248, 1805672, 3669120, 3713787, 3927600, 4321143, 4448880, 6928128 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..36.

MATHEMATICA

Do[ If[ Mod[ EulerPhi[ Prime[n] + 1], n] == 0, Print[n]], {n, 1, 10^7} ]

PROG

(PARI) isok(k) = (eulerphi(prime(k)+1) % k) == 0; \\ Michel Marcus, Feb 17 2021

CROSSREFS

Cf. A008331.

Sequence in context: A194393 A119260 A219616 * A334679 A222712 A117912

Adjacent sequences:  A067729 A067730 A067731 * A067733 A067734 A067735

KEYWORD

nonn,changed

AUTHOR

Benoit Cloitre, Feb 05 2002

EXTENSIONS

Edited and extended by Robert G. Wilson v, Feb 07 2002

STATUS

approved

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Last modified February 28 20:48 EST 2021. Contains 341731 sequences. (Running on oeis4.)