A103086 Numbers n such that 8*10^n + 5*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 8, 17, 19, 25, 40, 49, 58, 59, 92, 113, 296, 637, 1856, 2515, 3593, 6991, 11840, 86072, 93508

Offset

1,2

Comments

Also numbers n such that (77*10^n+31)/9 is prime.

a(22) > 10^5. - Robert Price, Oct 26 2015

Links

Table of n, a(n) for n=1..21.

Makoto Kamada, Prime numbers of the form 855...559.

Index entries for primes involving repunits.

Formula

a(n) = A101073(n) + 1.

Mathematica

Do[ If[ PrimeQ[(77*10^n + 31)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101073.

Sequence in context: A009662 A279243 A162218 * A192155 A131362 A370854

Adjacent sequences: A103083 A103084 A103085 * A103087 A103088 A103089

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(19) from Kamada data by Robert Price, Dec 14 2010

a(20)-a(21) from Robert Price, Oct 26 2015

Status

approved