Numbers k such that R_(k+2) + 5*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
A256931
Numbers k such that R_(k+2) + 5*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
Terms
- a(0) =3a(1) =16a(2) =24a(3) =165a(4) =270a(5) =478a(6) =1683a(7) =3976a(8) =41608a(9) =71760a(10) =86982a(11) =114226a(12) =116610a(13) =201504
External references
- oeis: A256931