A103085 Numbers n such that 8*10^n + 5*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 8, 1056, 19835, 20018, 36464, 81606

Offset

1,1

Comments

Also numbers n such that (77*10^n+13)/9 is prime.

a(8) > 10^5. - Robert Price, Oct 25 2015

Links

Table of n, a(n) for n=1..7.

Makoto Kamada, Prime numbers of the form 855...557.

Index entries for primes involving repunits.

Formula

a(n) = A101072(n) + 1.

Mathematica

Do[ If[ PrimeQ[(77*10^n + 13)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101072.

Sequence in context: A132573 A322142 A061591 * A084148 A014115 A014116

Adjacent sequences: A103082 A103083 A103084 * A103086 A103087 A103088

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(4)-a(6) from Kamada data by Robert Price, Dec 14 2010

a(7) from Robert Price, Oct 25 2015

Status

approved