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 A005937 Pseudoprimes to base 6. (Formerly M5246) 11
 35, 185, 217, 301, 481, 1105, 1111, 1261, 1333, 1729, 2465, 2701, 2821, 3421, 3565, 3589, 3913, 4123, 4495, 5713, 6533, 6601, 8029, 8365, 8911, 9331, 9881, 10585, 10621, 11041, 11137, 12209, 14315, 14701, 15841, 16589, 17329, 18361, 18721 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Theorem: If both numbers q and 2q-1 are primes and n=q*(2q-1) then 6^(n-1) == 1 (mod n) (n is in the sequence) iff q is of the form 12k+1. 2701, 18721, 49141, 104653, 226801, 665281, ... are such terms. This sequence is a subsequence of A122783. - Farideh Firoozbakht, Sep 12 2006 Composite numbers k such that 6^(k-1) == 1 (mod k). - Michel Lagneau, Feb 18 2012 REFERENCES R. K. Guy, Unsolved Problems in Number Theory, A12. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS R. J. Mathar, T. D. Noe, and Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 (Mathar 1..118, Noe 119..1000, Greathouse 1001..10000) C. Pomerance & N. J. A. Sloane, Correspondence, 1991 MATHEMATICA Select[Range[20000], ! PrimeQ[ # ] && PowerMod[6, #-1, # ] == 1 &] (* Farideh Firoozbakht, Sep 12 2006 *) CROSSREFS Cf. A001567 (pseudoprimes to base 2), A122783. Sequence in context: A220047 A101954 A220201 * A341043 A219831 A184200 Adjacent sequences:  A005934 A005935 A005936 * A005938 A005939 A005940 KEYWORD nonn AUTHOR EXTENSIONS More terms from Farideh Firoozbakht, Sep 12 2006 STATUS approved

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Last modified June 29 20:36 EDT 2022. Contains 354913 sequences. (Running on oeis4.)