Numbers k such that 2*R_k - 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A084832
Numbers k such that 2*R_k - 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =4a(1) =18a(2) =100a(3) =121a(4) =244a(5) =546a(6) =631a(7) =1494a(8) =2566a(9) =8088a(10) =262603a(11) =282948a(12) =359860
External references
- oeis: A084832