A093011 Primes of the form 10*R_k + 3, where R_k is the repunit (A002275) of length k.

3, 13, 113, 11113, 111111113, 11111111113, 111111111111111111111113, 111111111111111111111111111111111111111111111111111111111111111111111111111111111113

Offset: 1

Author

Rick L. Shepherd, Mar 14 2004

Keywords

• nonn

Comments

Primes of the form 2 + (10^k - 1)/9, k > 0. - Vincenzo Librandi, Dec 13 2011

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..9
• Makoto Kamada, Prime numbers of the form 11...113.
• Index entries for primes involving repunits

Crossrefs

Cf. A056654 (corresponding k).

Programs

Magma

[a: n in [1..100] | IsPrime(a) where a is ((10^n-1) div 9)+2 ]; // Vincenzo Librandi, Dec 13 2011

Mathematica

Select[Table[(((10^n-1)/ 9)+2),{n,1,900}],PrimeQ] (* Vincenzo Librandi, Dec 13 2011 *)