Numbers n such that 2*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A102960
Numbers n such that 2*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =2a(1) =12a(2) =27a(3) =44a(4) =80a(5) =119a(6) =131a(7) =275a(8) =315a(9) =876a(10) =1307a(11) =10895a(12) =17105a(13) =60717
External references
- oeis: A102960