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

1,1

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

Table of n, a(n) for n=1..6.

Makoto Kamada, Prime numbers of the form 55...553.

Index entries for primes involving repunits

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 *)

Crossrefs

Cf. A002275, A056685 (corresponding k).

Sequence in context: A173357 A144537 A208631 * A092448 A344424 A045481

Adjacent sequences: A093161 A093162 A093163 * A093165 A093166 A093167

Keyword

nonn

Author

Rick L. Shepherd, Mar 26 2004

Status

approved