Numbers n such that 4*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A102999
Numbers n such that 4*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =0a(1) =1a(2) =2a(3) =7a(4) =14a(5) =25a(6) =116a(7) =427a(8) =595a(9) =637a(10) =776a(11) =1706a(12) =16628a(13) =55558
External references
- oeis: A102999