Numbers n such that 5*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A103024
Numbers n such that 5*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =1a(1) =4a(2) =8a(3) =13a(4) =16a(5) =44a(6) =439a(7) =608a(8) =1201a(9) =2725a(10) =5210a(11) =59389a(12) =118216a(13) =198529
External references
- oeis: A103024