A103023 Numbers n such that 5*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 6, 8, 20, 108, 288, 306, 462, 20102, 30042, 69050

Offset

1,1

Comments

Also numbers n such that (53*10^n-17)/9 is prime.

a(12) > 10^5. - Robert Price, Sep 07 2015

Links

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

Makoto Kamada, Prime numbers of the form 588...887.

Index entries for primes involving repunits.

Formula

a(n) = A101588(n) + 1.

Mathematica

Do[ If[ PrimeQ[(53*10^n - 17)/9], Print[n]], {n, 0, 10000}]
Select[Range[0, 10000], PrimeQ[(53 10^# - 17)/9] &] (* Vincenzo Librandi, Sep 08 2015 *)

Prog

(Magma) [n: n in [0..350] | IsPrime((53*10^n-17) div 9)]; // Vincenzo Librandi, Sep 08 2015

Crossrefs

Cf. A002275, A101588.

Sequence in context: A290160 A290213 A058775 * A341732 A111247 A045656

Adjacent sequences: A103020 A103021 A103022 * A103024 A103025 A103026

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

Addition of a(9) from Kamada data by Robert Price, Dec 13 2010

a(10) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

a(11) from Robert Price, Sep 07 2015

Status

approved