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A067933 Primes p such that p == -1 (mod phi(p-1)). 2

%I

%S 2,3,5,7,11,31,71,2591,131071

%N Primes p such that p == -1 (mod phi(p-1)).

%C No more terms up to 373587883 (the 20 millionth prime).

%t Do[p = Prime[n]; If[ Mod[p + 1, EulerPhi[p - 1]] == 0, Print[p]], {n, 1, 10^8}] (* Cloitre *)

%t Select[Prime[Range[10^5]], Mod[#, EulerPhi[# - 1]] == EulerPhi[# - 1] - 1 &] (* _Alonso del Arte_, Sep 26 2011 *)

%K more,nonn

%O 1,1

%A _Benoit Cloitre_, Feb 22 2002

%E Edited by _Robert G. Wilson v_, Feb 27 2002

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Last modified October 27 10:47 EDT 2021. Contains 348274 sequences. (Running on oeis4.)