Numbers k such that 7*R_k + 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A098089
Numbers k such that 7*R_k + 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =2a(2) =66a(3) =86a(4) =90a(5) =102a(6) =386a(7) =624a(8) =7784a(9) =18536a(10) =113757a(11) =135879
External references
- oeis: A098089