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A163800
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a(n) is the n-th J_20-prime (Josephus_20 prime) Place the numbers 1..N (N>=2) on a circle and cyclicly mark the 20th unmarked number until all N numbers are marked. The order in which the N numbers are marked defines a permutation; N is a J_20-prime if this permutation consists of a single cycle of length N.
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18
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2, 5, 30, 54, 81, 109, 149, 186, 513, 1089, 8158, 8533, 17178, 34478, 913274, 976402
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| There are 16 J_20-primes in the interval 2..1000000 only. No formula is known; the J_20-primes were found by exhaustive search.
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REFERENCES
| R. L. Graham, D. E. Knuth & O. Patashnik, Concrete Mathematics (1989), Addison-Wesley, Reading, MA. Sections 1.3 & 3.3.
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LINKS
| P. R. J. Asveld, Permuting operations on strings and their relation to prime numbers, Discrete Applied Mathematics 159 (2011) 1915-1932.
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EXAMPLE
| 2 is a J_20-prime (trivial).
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CROSSREFS
| See A163782 through A163799 for J_2- through J_19-primes.
Sequence in context: A158866 A101078 A109739 * A180826 A019027 A019031
Adjacent sequences: A163797 A163798 A163799 * A163801 A163802 A163803
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KEYWORD
| nonn
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AUTHOR
| P. R. J. Asveld (infprja(AT)cs.utwente.nl), Aug 04 2009, Aug 12 2009
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