Numbers k such that 7*R_k + 10^k - 6 is prime, where R_k = 11...11 is the repunit (A002275) of length k.
A259121
Numbers k such that 7*R_k + 10^k - 6 is prime, where R_k = 11...11 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =6a(2) =48a(3) =102a(4) =192a(5) =366a(6) =1002a(7) =20364a(8) =37446a(9) =56082
External references
- oeis: A259121