

A158248


Composite numbers with primitive root 10.


2



49, 289, 343, 361, 529, 841, 2209, 2401, 3481, 3721, 4913, 6859, 9409, 11881, 12167, 12769, 16807, 17161, 22201, 24389, 27889, 32041, 32761, 37249, 49729, 52441, 54289, 66049, 69169, 72361, 83521, 97969
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OFFSET

1,1


COMMENTS

Previous name was: Numbers m whose reciprocal generates a repeating decimal fraction with period phi(m) and m/2 < phi(m) < m1.
All terms are proper powers of full reptend primes (A001913).
This sequence does not contain every proper power of every term in A001913, for example, A001913 has 487 as its 26th term, but since 10 is not a primitive root of 487^2, 487^2 is not a term of this sequence.  Robert Hutchins, Oct 14 2021
A shorter description appears to be "Composite numbers with primitive root 10".  Arkadiusz Wesolowski, Jul 04 2012 (The two definitions certainly produce the same terms up through 83521.  N. J. A. Sloane, Jul 05 2012)


LINKS



MAPLE

select(n > not isprime(n) and numtheory:primroot(9, n) = 10, [$2..10000]);


MATHEMATICA

Select[Range[10^5], GCD[10, #] == 1 && #/2 < MultiplicativeOrder[10, #] < #  1 &] (* Ray Chandler, Oct 17 2012 *)


CROSSREFS



KEYWORD

nonn,base


AUTHOR



EXTENSIONS



STATUS

approved



