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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
0, 5, 6, 185, 401, 480, 1319, 5646, 6029, 16824, 62387, 70638 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

a(13) > 10^5. - Robert Price, Oct 25 2015

LINKS

Table of n, a(n) for n=1..12.

Makoto Kamada, Prime numbers of the form 877...771.

Index entries for primes involving repunits.

FORMULA

a(n) = A101076(n+1) + 1, for n>1.

MATHEMATICA

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

CROSSREFS

Cf. A002275, A101076.

Sequence in context: A266718 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

Inserted a(1)=0 and added a(11)-a(12) by Robert Price, Oct 25 2015

STATUS

approved

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Last modified February 13 05:59 EST 2016. Contains 268240 sequences.