Numbers n such that 4*10^n + 2*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
A102986
Numbers n such that 4*10^n + 2*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
Terms
- a(0) =1a(1) =4a(2) =136a(3) =181a(4) =325a(5) =3292a(6) =3871a(7) =4690a(8) =7876a(9) =11911a(10) =16096a(11) =21649a(12) =43045
External references
- oeis: A102986