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A070738
Nonprimes n such that n^2 reduced modulo phi(n) = phi(n)^2 reduced modulo n.
1
1, 4, 8, 16, 18, 28, 30, 32, 36, 50, 54, 56, 64, 72, 75, 100, 102, 104, 108, 128, 144, 162, 200, 204, 208, 216, 234, 245, 250, 256, 288, 294, 306, 324, 400, 405, 408, 432, 486, 500, 512, 567, 576, 588, 612, 648, 693, 800, 864, 882, 900, 972, 990, 1000, 1024
OFFSET
1,2
COMMENTS
All powers of 2 are in the sequence.
LINKS
MATHEMATICA
Select[Range[1100], !PrimeQ[#]&&PowerMod[#, 2, EulerPhi[#]]== PowerMod[ EulerPhi[ #], 2, #]&] (* Harvey P. Dale, Feb 07 2016 *)
PROG
(PARI) for(n=1, 2000, if(n^2%eulerphi(n)*(-1)^isprime(n)==eulerphi(n)^2%n, print1(n, ", ")))
CROSSREFS
Sequence in context: A312782 A312783 A312784 * A055744 A141718 A195382
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, May 14 2002
STATUS
approved