

A103056


Numbers n such that 7*10^n + 3*R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1



0, 1, 2, 5, 7, 85, 345, 1595, 2105, 6386, 9119, 9332, 14707, 72560
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OFFSET

1,3


COMMENTS

Also numbers n such that (22*10^n+17)/3 is prime.
a(15) > 10^5.  Robert Price, Sep 26 2015


LINKS

Table of n, a(n) for n=1..14.
Makoto Kamada, Prime numbers of the form 733...339.
Index entries for primes involving repunits.


FORMULA

a(n) = A101138(n1) + 1 for n>1.


EXAMPLE

For n=0, (22*10^n+17)/3 = 13 which is a prime so 0 is a term.


MATHEMATICA

Do[ If[ PrimeQ[(22*10^n + 17)/3], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A101138.
Sequence in context: A293592 A042257 A343833 * A041445 A265815 A041961
Adjacent sequences: A103053 A103054 A103055 * A103057 A103058 A103059


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 19 2005


EXTENSIONS

a(13) from Kamada data by Robert Price, Dec 14 2010
Inserted a(1) = 0 by Robert Price, Sep 26 2015
a(14) from Robert Price, Sep 26 2015


STATUS

approved



