Numbers k such that 9*R_(k+2) - 2*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A257040
Numbers k such that 9*R_(k+2) - 2*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =0a(1) =90a(2) =1928a(3) =2206a(4) =7244a(5) =11110a(6) =125056a(7) =131394a(8) =301354
External references
- oeis: A257040