

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
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OFFSET

1,2


COMMENTS

Also numbers n such that (79*10^n61)/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



