A093405 Primes of the form 80*R_k + 9, where R_k is the repunit (A002275) of length k.

89, 88888888888889, 88888888888888889, 88888888888888888888888888888888889

Offset: 1

Author

Rick L. Shepherd, Mar 28 2004

Keywords

• nonn

Comments

Primes of the form (8*10^k + 1)/9. - Vincenzo Librandi, Jul 17 2012

Links

• Makoto Kamada, Prime numbers of the form 88...889.
• Index entries for primes involving repunits

Crossrefs

Cf. A056663 (corresponding k).

Programs

Mathematica

Select[Table[(8*10^n+1)/9,{n,1,200}],PrimeQ] (* Vincenzo Librandi, Jul 17 2012 *)
Select[Table[FromDigits[PadLeft[{9},n,8]],{n,100}],PrimeQ] (* Harvey P. Dale, Dec 15 2023 *)