Numbers k such that 3*10^k + 5*R_k - 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A102971
Numbers k such that 3*10^k + 5*R_k - 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =6a(2) =9a(3) =15a(4) =24a(5) =48a(6) =73a(7) =75a(8) =97a(9) =249a(10) =273a(11) =2488a(12) =14499a(13) =74773a(14) =87448
External references
- oeis: A102971