Numbers k such that 7*10^k + 3*R_k - 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

A103055

Numbers k such that 7*10^k + 3*R_k - 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

Terms

    a(0) =1a(1) =3a(2) =4a(3) =5a(4) =6a(5) =9a(6) =12a(7) =31a(8) =59a(9) =69a(10) =74a(11) =287a(12) =489a(13) =592a(14) =634a(15) =1089a(16) =1607a(17) =3141a(18) =5962a(19) =6267a(20) =9678a(21) =11431a(22) =12927a(23) =32189a(24) =38700a(25) =53033a(26) =83525a(27) =185950

External references