A059109 - OEIS

A059109

Numbers m such that m*phi(m)-1 is prime, where phi is the Euler function (A000010).

3, 4, 5, 6, 7, 8, 9, 11, 12, 14, 16, 17, 18, 21, 24, 25, 26, 29, 30, 31, 33, 35, 36, 38, 42, 47, 54, 61, 63, 65, 66, 67, 71, 74, 75, 78, 81, 87, 91, 97, 99, 101, 105, 117, 119, 121, 123, 127, 128, 131, 132, 135, 139, 140, 143, 144, 147, 149, 154, 156, 158, 162, 172

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OFFSET

1,1

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

MATHEMATICA

Select[Range[200], PrimeQ[# EulerPhi[#]-1]&] (* Harvey P. Dale, Aug 23 2012 *)

PROG

(PARI) is(n)=isprime(n*eulerphi(n)-1) \\ Charles R Greathouse IV, Feb 21 2013

(Magma) [n: n in [1..200] | IsPrime(n*EulerPhi(n)-1)]; // Vincenzo Librandi, Jul 31 2018

CROSSREFS

Cf. A000010, A046078.