A103051 Numbers n such that 7*10^n + R_n + 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 4, 17, 25, 32, 50, 74, 173, 1724, 2084, 11398

Offset

1,2

Comments

Also numbers n such that (64*10^n+71)/9 is prime.

a(13) > 10^5. - Robert Price, Sep 21 2015

Links

Table of n, a(n) for n=1..12.

Makoto Kamada, Prime numbers of the form 711...119.

Index entries for primes involving repunits.

Formula

a(n) = A101132(n) + 1.

Mathematica

Do[ If[ PrimeQ[(64*10^n + 71)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101132.

Sequence in context: A006276 A318367 A317488 * A095018 A081356 A018269

Adjacent sequences: A103048 A103049 A103050 * A103052 A103053 A103054

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(12) from Kamada data by Robert Price, Dec 14 2010

Status

approved