Numbers k such that R_(k+2) + 2*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A256926
Numbers k such that 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) =1a(2) =4a(3) =7a(4) =16a(5) =19a(6) =37a(7) =67a(8) =166a(9) =292a(10) =20941
External references
- oeis: A256926