OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
MATHEMATICA
pr = 15; Select[Range[2, 500], MultiplicativeOrder[pr, #] == EulerPhi[#] &]
Join[{2, 4, 13}, Select[Range[2, 400], PrimitiveRoot[#, 15]==15&]] (* Harvey P. Dale, Jun 30 2018 *)
CROSSREFS
Cf. numbers with positive primitive root r: A167791 (r=2), A167792 (r=3), A167793 (r=5), A167794 (r=6), A167795 (r=7), A167796 (r=8), A167797 (r=10), A240028 (r=11), A240030 (r=12), A240032 (r=13), A240094 (r=14).
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Apr 01 2014
STATUS
approved