

A103101


Numbers n such that 9*10^n + 5*R_n  2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1




OFFSET

1,2


COMMENTS

Also numbers n such that (86*10^n23)/9 is prime.
a(9) > 10^5.  Robert Price, Nov 08 2015


LINKS

Table of n, a(n) for n=1..8.
Makoto Kamada, Prime numbers of the form 955...553.
Index entries for primes involving repunits.


FORMULA

a(n) = A101010(n1) + 1, for n>1.


MATHEMATICA

Do[ If[ PrimeQ[(86*10^n  23)/9], Print[n]], {n, 0, 10000}]


PROG

(PARI) for(n=0, 1e5, if(isprime((86*10^n23)/9), print1(n, ", "))); \\ Altug Alkan, Nov 08 2015


CROSSREFS

Cf. A002275, A101010.
Sequence in context: A220856 A035599 A222556 * A267678 A009357 A052361
Adjacent sequences: A103098 A103099 A103100 * A103102 A103103 A103104


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 19 2005


EXTENSIONS

a(8) from Kamada data by Robert Price, Dec 14 2010
Inserted a(1)=0 by Robert Price, Nov 08 2015


STATUS

approved



