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A000236
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Maximum m such that there are no two adjacent elements belonging to the same n-th power residue class modulo some prime p in the sequence 1,2,...,m (equivalently, there is no n-th power residue modulo p in the sequence 1/2,2/3,...,(m-1)/m).
(Formerly M2737 N1099)
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4
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3, 8, 20, 44, 80, 343, 288, 608, 1023, 2848, 4095, 40959, 16383, 32768, 11375, 655360, 262143, 3670016, 1048575, 2097151
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OFFSET
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2,1
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COMMENTS
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Rabung and Jordan (1970) incorrectly computed a(8) as 399: their placement of residues supporting a(8)=399 fails since 80 and 81 fall into the same 8th-power residue class. - Max Alekseyev, Aug 10 2005
Don Reble pointed out that for even n, the n-th residue class placement of prime factors q of n must obey the quadratic reciprocity law: q must be in an even class whenever n*(q-1) is a multiple of 8. - Max Alekseyev, Sep 04 2017
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REFERENCES
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N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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If 8|n, a(n) >= 2^(n/2) - 1; otherwise a(n) >= 2^n - 1. - Max Alekseyev, Aug 10 2005; corrected Sep 04, 2017.
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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a(8) corrected and a(9)-a(16) added by Max Alekseyev, Aug 10 2005
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STATUS
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approved
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