Numbers k such that 7*R_k - 30 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A256829
Numbers k such that 7*R_k - 30 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =2a(1) =5a(2) =8a(3) =13a(4) =17a(5) =50a(6) =169a(7) =193a(8) =407a(9) =1496a(10) =1718a(11) =3610a(12) =6527a(13) =6889a(14) =12665a(15) =15949a(16) =23498a(17) =32969a(18) =44773a(19) =110027
External references
- oeis: A256829