Numbers k such that 50*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A056686
Numbers k such that 50*R_k + 7 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =2a(2) =3a(3) =5a(4) =9a(5) =14a(6) =21a(7) =87a(8) =206a(9) =527a(10) =959a(11) =2099a(12) =18521a(13) =36782a(14) =38516
External references
- oeis: A056686