Numbers k such that 10^k + 2*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A102930
Numbers k such that 10^k + 2*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =2a(2) =4a(3) =14a(4) =25a(5) =32a(6) =56a(7) =62a(8) =811a(9) =812a(10) =1084a(11) =2533a(12) =11924a(13) =49552
External references
- oeis: A102930