A216346 Primes of the form n*10^n - 1.

199, 2999, 799999999, 1099999999999, 14999999999999999, 38999999999999999999999999999999999999999, 59999999999999999999999999999999999999999999999999999999999999, 71999999999999999999999999999999999999999999999999999999999999999999999999

Offset: 1

Author

Michel Lagneau, Sep 04 2012

Keywords

• nonn

Comments

The corresponding n are in A059671.

a(9) = 769999999….999999 contains 79 digits.

a(10) = 1169999999….999999 contains 120 digits.

Crossrefs

Cf. A059671.

Programs

Mathematica

lst={}; Do[ p=n*10^n- 1; If[PrimeQ[p], AppendTo[lst, p]], {n, 0, 60}]; lst
Select[Table[n*10^n-1,{n,100}],PrimeQ] (* Harvey P. Dale, Sep 17 2023 *)