A103043 Numbers n such that 6*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

3, 5, 15, 47, 69, 123, 713, 2316, 6147, 8877, 10704

Offset

1,1

Comments

Also numbers n such that (61*10^n+11)/9 is prime.

a(12) > 10^5. - Robert Price, Sep 15 2015

Links

Table of n, a(n) for n=1..11.

Makoto Kamada, Prime numbers of the form 677...779.

Index entries for primes involving repunits.

Formula

a(n) = A101536(n) + 1.

Mathematica

Do[ If[ PrimeQ[(61*10^n + 11)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101536.

Sequence in context: A018568 A371903 A038375 * A018601 A190733 A211344

Adjacent sequences: A103040 A103041 A103042 * A103044 A103045 A103046

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

a(11) from Kamada data by Robert Price, Dec 14 2010

Status

approved