A093164 Primes of the form 50*R_k + 3, where R_k is the repunit (A002275) of length k.

3, 53, 55555553, 55555555555555555555555553, 555555555555555555555555555555555555555555555555555555555555555553, 55555555555555555555555555555555555555555555555555555555555555555555555553

Offset: 1

Author

Rick L. Shepherd, Mar 26 2004

Keywords

• nonn

Comments

Primes of the form (5*10^k - 23)/9. - Vincenzo Librandi, Nov 16 2010

The next term (a(7)) has 233 digits. - Harvey P. Dale, Mar 04 2024

Links

• Makoto Kamada, Prime numbers of the form 55...553.
• Index entries for primes involving repunits

Crossrefs

Cf. A002275, A056685 (corresponding k).

Programs

Mathematica

Select[(5(10^Range[74])-23)/9,PrimeQ] (* Paul F. Marrero Romero, Oct 20 2023 *)
Select[Table[FromDigits[PadLeft[{3},n,5]],{n,75}],PrimeQ] (* Harvey P. Dale, Mar 04 2024 *)