

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




OFFSET

1,1


COMMENTS

Also numbers n such that (79*10^n61)/9 is prime.


LINKS

Table of n, a(n) for n=1..9.
Makoto Kamada, Prime numbers of the form 877...771.
Index entries for primes involving repunits.


FORMULA

a(n) = A101076(n) + 1.


MATHEMATICA

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


CROSSREFS

Cf. A002275, A101076.
Sequence in context: A078984 A041257 A041411 * A041601 A041827 A042089
Adjacent sequences: A103086 A103087 A103088 * A103090 A103091 A103092


KEYWORD

more,nonn,changed


AUTHOR

Robert G. Wilson v, Jan 19 2005


EXTENSIONS

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


STATUS

approved



