Numbers k such that 3*10^k + 6*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

A102974

Numbers k such that 3*10^k + 6*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

Terms

    a(0) =1a(1) =6a(2) =11a(3) =13a(4) =19a(5) =23a(6) =67a(7) =108a(8) =118a(9) =176a(10) =673a(11) =780a(12) =1088a(13) =1219a(14) =1656a(15) =6245a(16) =10739a(17) =12590a(18) =17513a(19) =26000a(20) =32544a(21) =53274a(22) =131784

External references