Numbers k such that 10*R_k + 9 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056659
Numbers k such that 10*R_k + 9 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =4a(2) =5a(3) =7a(4) =16a(5) =49a(6) =683a(7) =719a(8) =1451a(9) =1678a(10) =3145a(11) =72820a(12) =111901a(13) =146062a(14) =180688a(15) =330905
External references
- oeis: A056659