

A103042


Numbers n such that 6*10^n + 7*R_n  4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1




OFFSET

1,2


COMMENTS

Also numbers n such that (61*10^n43)/9 is prime.
a(11) > 10^5.  Robert Price, Sep 12 2015


LINKS

Table of n, a(n) for n=1..10.
Makoto Kamada, Prime numbers of the form 677...773.
Index entries for primes involving repunits.


FORMULA

a(n) = A101535(n1) + 1 for n>1.


MATHEMATICA

Do[ If[ PrimeQ[(61*10^n  43)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A101535.
Sequence in context: A332585 A000725 A151614 * A284458 A260886 A142006
Adjacent sequences: A103039 A103040 A103041 * A103043 A103044 A103045


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 18 2005


EXTENSIONS

a(8)a(9) from Kamada data by Robert Price, Dec 14 2010
Inserted a(1)=0 by Robert Price, Sep 12 2015
a(10) from Robert Price, Sep 12 2015


STATUS

approved



