

A103066


Numbers n such that 7*10^n + 8*R_n  5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1



0, 1, 3, 6, 60, 288, 1314, 1728, 2493, 13893, 13944, 17100, 70227
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OFFSET

1,3


COMMENTS

Also numbers n such that (71*10^n53)/9 is prime.
a(14) > 10^5.  Robert Price, Oct 06 2015


LINKS

Table of n, a(n) for n=1..13.
Makoto Kamada, Prime numbers of the form 788...883.
Index entries for primes involving repunits.


FORMULA

a(n) = A101151(n1) + 1 for n>1.


EXAMPLE

For n=0, (71*10^n53)/9 = 2 which is prime.


MATHEMATICA

Do[ If[ PrimeQ[(71*10^n  53)/9], Print[n]], {n, 0, 10000}]


PROG

(PARI) for(n=0, 10^5, if(isprime((71*10^n53)/9), print1(n", "))); \\ Altug Alkan, Oct 06 2015


CROSSREFS

Cf. A002275, A101151.
Sequence in context: A012473 A058161 A012877 * A145887 A219809 A137123
Adjacent sequences: A103063 A103064 A103065 * A103067 A103068 A103069


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 19 2005


EXTENSIONS

a(10)a(12) from Kamada data by Robert Price, Dec 14 2010
Inserted a(1)=0 and added a(13) by Robert Price, Oct 06 2015


STATUS

approved



