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A069069
Numbers n such that n*phi(n-1) is a perfect square.
1
9, 27, 45, 49, 64, 486, 637, 867, 961, 1035, 1352, 1408, 1521, 3971, 4913, 7581, 8750, 12936, 14283, 19602, 20825, 23104, 36481, 43681, 44506, 48600, 49005, 58621, 63001, 72897, 75843, 85697, 90168, 97470, 108241, 122317, 127008
OFFSET
1,1
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..1000
MATHEMATICA
Rest[Select[Range[130000], IntegerQ[Sqrt[# EulerPhi[#-1]]]&]] (* Harvey P. Dale, Jun 08 2013 *)
PROG
(PARI) is(n)=issquare(eulerphi(n-1)*n) \\ Charles R Greathouse IV, Sep 21 2016
CROSSREFS
Sequence in context: A103753 A238333 A103965 * A354815 A031088 A020156
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Apr 05 2002
STATUS
approved