Numbers n such that 2*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A102962
Numbers n such that 2*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =3a(1) =6a(2) =18a(3) =69a(4) =443a(5) =449a(6) =455a(7) =2459a(8) =4745a(9) =7973a(10) =14249a(11) =31710
External references
- oeis: A102962