Numbers k such that 50*R_k + 9 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056687
Numbers k such that 50*R_k + 9 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =7a(2) =11a(3) =17a(4) =25a(5) =31a(6) =137a(7) =187a(8) =221a(9) =337a(10) =1001a(11) =2743a(12) =6529a(13) =38689a(14) =39463
External references
- oeis: A056687