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A179077
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a(n) is the residue ((2^p - 2)/p) mod p, where p is the n-th prime.
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1
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1, 2, 1, 4, 10, 6, 9, 6, 11, 2, 12, 2, 5, 7, 41, 19, 16, 11, 20, 4, 39, 38, 13, 12, 17, 83, 15, 26, 25, 53, 36, 34, 106, 60, 43, 112, 7, 134, 94, 6, 100, 115, 100, 15, 153, 71, 7, 155, 175, 136, 14, 52, 43, 243, 193, 256, 251, 218, 140, 148, 116, 156, 281, 39, 240, 33, 278
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OFFSET
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1,2
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COMMENTS
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a(n) = 0 where n=183 (p=1093) and n=490 (p=3511).
Conjecture: a(n) is the residue A036968(p-1) (mod p) for p = prime(n).
If the above conjecture is true, then a(n) = 0 if and only if p is a Wieferich prime (A001220) (cf. Hu et al., 2019, section 1.3). (End)
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LINKS
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MATHEMATICA
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aa = {}; Do[AppendTo[aa, Mod[(2^Prime[n] - 2)/Prime[n], Prime[n]]], {n, 1, 100}]; aa
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PROG
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(PARI) a(n) = my(p=prime(n)); lift(Mod(((2^p-2)/p), p)) \\ Felix Fröhlich, Sep 13 2019
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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