

A163787


a(n) is the nth J_7prime (Josephus_7 prime).


2



5, 11, 21, 35, 85, 103, 161, 231, 543, 1697, 1995, 2289, 37851, 49923, 113443, 236091, 285265
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OFFSET

1,1


COMMENTS

Place the numbers 1..N (N>=2) on a circle and cyclicly mark the 7th unmarked number until all N numbers are marked. The order in which the N numbers are marked defines a permutation; N is a J_7prime if this permutation consists of a single cycle of length N.
There are 17 J_7primes in the interval 2..1000000 only. No formula is known; the J_7primes have been found by exhaustive search.


REFERENCES

P. R. J. Asveld, Permuting Operations on StringsTheir Permutations and Their Primes, Twente University of Technology, 2014; http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.216.1682; http://doc.utwente.nl/67513/1/pospp.pdf.
R. L. Graham, D.E. Knuth & O. Patashnik, Concrete Mathematics (1989), AddisonWesley, Reading, MA. Sections 1.3 & 3.3.


LINKS

Table of n, a(n) for n=1..17.
P. R. J. Asveld, Permuting Operations on Strings and Their Relation to Prime Numbers, Discrete Applied Mathematics 159 (2011) 19151932.


EXAMPLE

All J_7primes are odd.


CROSSREFS

A163782 through A163786 for J_2 through J_6primes. A163788 through A163800 for J_8 through J_20primes.
Sequence in context: A166480 A164096 A298785 * A166863 A163704 A131898
Adjacent sequences: A163784 A163785 A163786 * A163788 A163789 A163790


KEYWORD

nonn,more


AUTHOR

Peter R. J. Asveld, Aug 05 2009


STATUS

approved



