A103091 Numbers n such that 8*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 3, 6, 31, 36, 61, 117, 229, 339, 3165, 3958, 5277, 5343, 6079, 6535, 8485, 15084, 34537

Offset

1,2

Comments

Also numbers n such that (79*10^n+11)/9 is prime.

a(19) > 10^5. - Robert Price, Oct 27 2015

Links

Table of n, a(n) for n=1..18.

Makoto Kamada, Prime numbers of the form 877...779.

Index entries for primes involving repunits.

Formula

a(n) = A101078(n) + 1.

Mathematica

Do[ If[ PrimeQ[(79*10^n + 11)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101078.

Sequence in context: A117805 A154135 A182274 * A186940 A101751 A274999

Adjacent sequences: A103088 A103089 A103090 * A103092 A103093 A103094

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(17) from Kamada data by Robert Price, Dec 14 2010

a(18) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

Status

approved