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A056213
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Primes p for which the period of reciprocal = (p-1)/8.
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13
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41, 241, 1601, 1609, 2441, 2969, 3041, 3449, 3929, 4001, 4409, 5009, 6089, 6521, 6841, 8161, 8329, 8609, 9001, 9041, 9929, 13001, 13241, 14081, 14929, 16001, 16481, 17489, 17881, 18121, 19001, 20249, 20641, 20921, 21529, 22481, 23801
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OFFSET
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1,1
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COMMENTS
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Cyclic numbers of the eighth degree (or eighth order): the reciprocals of these numbers belong to one of eight different cycles. Each cycle has the (number minus 1)/8 digits.
All terms == 1 (mod 8). (End)
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LINKS
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MAPLE
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select(t -> isprime(t) and numtheory:-order(10, t) = (t-1)/8, [seq(t, t=17..24000, 8)]); # Robert Israel, Apr 02 2018
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MATHEMATICA
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f[n_Integer] := Block[{ds = Divisors[n - 1]}, (n - 1)/Take[ ds, Position[ PowerMod[ 10, ds, n], 1] [[1, 1]]] [[ -1]]]; Select[ Prime[ Range[4, 2700]], f[ # ] == 8 &]
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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