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Numbers with primitive root 5.
19

%I #7 Jan 04 2025 00:36:49

%S 2,3,6,7,9,14,17,18,23,27,34,37,43,46,47,49,53,54,73,74,81,83,86,94,

%T 97,98,103,106,107,113,137,146,157,162,166,167,173,193,194,197,206,

%U 214,223,226,227,233,243,257,263,274,277,283,289,293,307,314,317,334,343,346

%N Numbers with primitive root 5.

%H Vincenzo Librandi, <a href="/A167793/b167793.txt">Table of n, a(n) for n = 1..1000</a>

%t pr=5; Select[Range[2,2000], MultiplicativeOrder[pr,# ] == EulerPhi[ # ] &]

%o (PARI) is(n)=if(n%5==0, return(0)); my(p=eulerphi(n)); znorder(Mod(5, n), p)==p \\ _Charles R Greathouse IV_, Jan 04 2025

%Y Cf. A019335 (primes with primitive root 5)

%K nonn

%O 1,1

%A _T. D. Noe_, Nov 12 2009