Numbers k such that 8*R_k + 9*10^k + 1 is prime, where R_k = 11...11 is the repunit (A002275) of length k.
A259139
Numbers k such that 8*R_k + 9*10^k + 1 is prime, where R_k = 11...11 is the repunit (A002275) of length k.
Terms
- a(0) =6a(1) =72a(2) =96a(3) =114a(4) =204a(5) =984a(6) =1226a(7) =4794a(8) =20720a(9) =133580a(10) =411590
External references
- oeis: A259139