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A103089 Numbers n such that 8*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
5, 6, 185, 401, 480, 1319, 5646, 6029, 16824 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also numbers n such that (79*10^n-61)/9 is prime.

LINKS

Table of n, a(n) for n=1..9.

Makoto Kamada, Factorizations of 877...771.

Index entries for primes involving repunits.

MATHEMATICA

Do[ If[ PrimeQ[(79*10^n - 61)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Sequence in context: A078984 A041257 A041411 * A041601 A041827 A042089

Adjacent sequences:  A103086 A103087 A103088 * A103090 A103091 A103092

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 19 2005

EXTENSIONS

1 more term. Next term exceeds 50000. Sean A. Irvine, Sep 10 2009

STATUS

approved

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Last modified July 29 21:54 EDT 2014. Contains 245046 sequences.