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

A056704

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

Terms

    a(0) =0a(1) =1a(2) =2a(3) =5a(4) =10a(5) =11a(6) =13a(7) =34a(8) =47a(9) =52a(10) =77a(11) =88a(12) =554a(13) =580a(14) =1310a(15) =1505a(16) =8537a(17) =15892a(18) =24022a(19) =27041a(20) =37922a(21) =40033a(22) =134122a(23) =165358a(24) =183760

External references