A067732 Numbers k such that phi(prime(k) + 1) == 0 (mod k).

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

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..72

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
(PARI) list(lim) = my(k = 0); forprime(p = 1, lim, k++; if(!(eulerphi(p+1) % k), print1(k, ", "))); \\ Amiram Eldar, Apr 25 2025

Crossrefs

Cf. A008331.

Sequence in context: A194393 A119260 A219616 * A334679 A222712 A117912

Adjacent sequences: A067729 A067730 A067731 * A067733 A067734 A067735

Keyword

nonn

Author

Benoit Cloitre, Feb 05 2002

Extensions

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

Status

approved