Numbers k such that 5*10^k + 3*R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056714
Numbers k such that 5*10^k + 3*R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =1a(2) =3a(3) =13a(4) =25a(5) =49a(6) =143a(7) =419a(8) =1705a(9) =13993a(10) =35753a(11) =40889
External references
- oeis: A056714