A093163 Primes of the form 40*R_k + 3, where R_k is the repunit (A002275) of length k.

3, 43, 443, 444443, 444444443, 444444444443, 444444444444444444444444444443, 44444444444444444444444444444443

Offset: 1

Author

Rick L. Shepherd, Mar 26 2004

Keywords

• nonn

Comments

Primes of the form (4*10^k - 13)/9; the next term a(9) is a 183-digit number. - Vincenzo Librandi, Nov 16 2010

Links

• Makoto Kamada, Prime numbers of the form 44...443.
• Index entries for primes involving repunits

Crossrefs

Cf. A056661 (corresponding k), A173770.

Programs

Mathematica

f[n_] := (4*10^n-13)/9; Select[f[Range[50]], PrimeQ] (* Amiram Eldar, Nov 23 2018 *)
Select[Table[FromDigits[PadLeft[{3},n,4]],{n,40}],PrimeQ] (* Harvey P. Dale, Dec 19 2022 *)