Numbers k such that 5*R_k - 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A099416
Numbers k such that 5*R_k - 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =2a(2) =8a(3) =26a(4) =66a(5) =74a(6) =233a(7) =473a(8) =540a(9) =2774a(10) =64715a(11) =102492a(12) =141594
External references
- oeis: A099416