Numbers k such that 3*10^k + 8*R_k - 7 is a prime, where R_k = 11...1 is the repunit (A002275) of length k.

A102978

Numbers k such that 3*10^k + 8*R_k - 7 is a prime, where R_k = 11...1 is the repunit (A002275) of length k.

Terms

    a(0) =1a(1) =3a(2) =19a(3) =30a(4) =40a(5) =42a(6) =45a(7) =70a(8) =307a(9) =538a(10) =1609a(11) =1668a(12) =1674a(13) =4492a(14) =4935a(15) =6112a(16) =12819a(17) =14079a(18) =16020a(19) =23005a(20) =50997a(21) =82870

External references