Numbers k such that R_(k+2) + 7*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A256933
Numbers k such that R_(k+2) + 7*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =1a(1) =2a(2) =11a(3) =62a(4) =157a(5) =170a(6) =251a(7) =500a(8) =2275a(9) =7525a(10) =12230a(11) =13658a(12) =54727a(13) =183227a(14) =212779
External references
- oeis: A256933