Numbers k such that 2*R_k + 7*10^k + 5 is prime, where R_k = 11...11 is the repunit (A002275) of length k.
A259135
Numbers k such that 2*R_k + 7*10^k + 5 is prime, where R_k = 11...11 is the repunit (A002275) of length k.
Terms
- a(0) =2a(1) =4a(2) =8a(3) =28a(4) =64a(5) =724a(6) =1786a(7) =7276a(8) =19462a(9) =24214a(10) =51778a(11) =131392
External references
- oeis: A259135