

A103074


Numbers n such that 8*10^n + 2*R_n  1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1




OFFSET

1,2


COMMENTS

Also numbers n such that (74*10^n11)/9 is prime.
a(10) > 10^5.  Robert Price, Oct 13 2015


LINKS

Table of n, a(n) for n=1..9.
Makoto Kamada, Prime numbers of the form 822...221.
Index entries for primes involving repunits.


FORMULA

a(n) = A101061(n1) + 1 for n>1.


MATHEMATICA

Do[ If[ PrimeQ[(74*10^n  11)/9], Print[n]], {n, 0, 10000}]


PROG

(PARI) for(n=0, 50000, if(isprime((74*10^n11)/9), print1(n", "))) \\ Altug Alkan, Oct 13 2015


CROSSREFS

Cf. A002275, A101061.
Sequence in context: A019350 A235630 A235636 * A173236 A245641 A082979
Adjacent sequences: A103071 A103072 A103073 * A103075 A103076 A103077


KEYWORD

more,nonn,changed


AUTHOR

Robert G. Wilson v, Jan 19 2005


EXTENSIONS

a(9) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
Inserted a(1)=0 by Robert Price, Oct 13 2015


STATUS

approved



