Numbers k such that 2*10^k + 8*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A102961
Numbers k such that 2*10^k + 8*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =2a(2) =7a(3) =28a(4) =73a(5) =295a(6) =494a(7) =598a(8) =2600a(9) =3730a(10) =7549a(11) =15865
External references
- oeis: A102961