

A122783


Nonprimes n such that 6^n==6 (mod n).


3



1, 6, 10, 15, 21, 30, 35, 105, 185, 190, 217, 231, 301, 430, 435, 481, 561, 777, 1105, 1111, 1221, 1261, 1333, 1729, 1866, 2121, 2465, 2553, 2701, 2821, 2955, 3421, 3565, 3589, 3885, 3913, 4123, 4495, 5061, 5565, 5662, 5713, 6531, 6533, 6601
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OFFSET

1,2


COMMENTS

Theorem: If both numbers q and 2q1 are primes then n=q*(2q1) is in the sequence iff q<5 or q is of the form 12k+1. 6,15,2701,18721,49141,104653,226801,665281,... are such terms.


LINKS

Table of n, a(n) for n=1..45.


MATHEMATICA

Select[Range[7000], ! PrimeQ[ # ] && Mod[6^#, # ] == Mod[6, # ] &]


CROSSREFS

Cf. A005937.
Sequence in context: A115744 A211007 A315279 * A124000 A229321 A229323
Adjacent sequences: A122780 A122781 A122782 * A122784 A122785 A122786


KEYWORD

easy,nonn


AUTHOR

Farideh Firoozbakht, Sep 12 2006


STATUS

approved



