Numbers n such that 9*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

A103109

Numbers n such that 9*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) =3a(2) =4a(3) =6a(4) =9a(5) =12a(6) =16a(7) =34a(8) =129a(9) =243a(10) =252a(11) =529a(12) =4885a(13) =6363a(14) =12951a(15) =13188a(16) =29931a(17) =34888a(18) =49516a(19) =67431a(20) =77781

External references