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A122783
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Nonprimes n such that 6^n==6 (mod n).
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2
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Theorem: If both numbers q and 2q-1 are primes then n=q*(2q-1) 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.
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MATHEMATICA
| Select[Range[7000], ! PrimeQ[ # ] && Mod[6^#, # ] == Mod[6, # ] &]
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CROSSREFS
| Cf. A005937.
Sequence in context: A080255 A168102 A115744 * A124000 A068443 A113940
Adjacent sequences: A122780 A122781 A122782 * A122784 A122785 A122786
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KEYWORD
| easy,nonn
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AUTHOR
| Farideh Firoozbakht (mymontain(AT)yahoo.com), Sep 12 2006
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