A070738 Nonprimes n such that n^2 reduced modulo phi(n) = phi(n)^2 reduced modulo n.

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

Harvey P. Dale, Table of n, a(n) for n = 1..1000

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

Adjacent sequences: A070735 A070736 A070737 * A070739 A070740 A070741

Keyword

easy,nonn

Author

Benoit Cloitre, May 14 2002

Status

approved