Numbers k such that 9*10^k + R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056726
Numbers k such that 9*10^k + R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =2a(1) =5a(2) =20a(3) =41a(4) =47a(5) =92a(6) =161a(7) =401a(8) =455a(9) =8570a(10) =18592a(11) =73714a(12) =78635a(13) =100780
External references
- oeis: A056726