Numbers k such that 7*10^k + 2*R_k - 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A103052
Numbers k such that 7*10^k + 2*R_k - 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =4a(2) =16a(3) =25a(4) =29a(5) =41a(6) =47a(7) =88a(8) =1132a(9) =1570a(10) =3985a(11) =10609a(12) =12175a(13) =29369
External references
- oeis: A103052