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A108989
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Composite numbers n with primitive root 2; i.e. the order of 2 modulo n is phi(n).
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0
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9, 25, 27, 81, 121, 125, 169, 243, 361, 625, 729, 841, 1331, 1369, 2187, 2197, 2809, 3125, 3481, 3721, 4489, 6561, 6859, 6889, 10201, 11449, 14641, 15625, 17161, 19321, 19683, 22201, 24389, 26569, 28561, 29929, 32041, 32761, 38809, 44521, 50653
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| Modulo 9: 2^1=2, 2^2=4, 2^3=8, 2^4=7, 2^5=5, 2^6=1 and Phi(9)=6.
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MATHEMATICA
| nn=51000; Select[Complement[Range[2, nn], Prime[Range[PrimePi[nn]]]], PrimitiveRoot[#]==2&] (* From Harvey P. Dale, Jul 25 2011 *)
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PROG
| (GAP) for i in [2..100000] do if not IsPrime(i) then if IsPrimitiveRootMod(2, i) then Display(i); fi; fi; od;
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CROSSREFS
| Cf. A001122.
Sequence in context: A075109 A117580 A020308 * A068583 A074852 A020252
Adjacent sequences: A108986 A108987 A108988 * A108990 A108991 A108992
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KEYWORD
| nonn
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AUTHOR
| Douglas Stones (dssto1(AT)student.monash.edu.au), Jul 28 2005
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