Numbers k such that 9*R_k + 10^k - 8 is prime, where R_k = 11...11 is the repunit (A002275) of length k.
A259120
Numbers k such that 9*R_k + 10^k - 8 is prime, where R_k = 11...11 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =2a(2) =4a(3) =8a(4) =40a(5) =86a(6) =200a(7) =730a(8) =1460a(9) =23672a(10) =28630
External references
- oeis: A259120