Numbers k such that 7*10^k + 5*R_k + 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A103062
Numbers k such that 7*10^k + 5*R_k + 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =1a(2) =3a(3) =237a(4) =243a(5) =351a(6) =967a(7) =1843a(8) =7405a(9) =9633a(10) =59821
External references
- oeis: A103062