Numbers k such that 2*10^k + 6*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

A098959

Numbers k such that 2*10^k + 6*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

Terms

    a(0) =1a(1) =2a(2) =3a(3) =5a(4) =6a(5) =7a(6) =11a(7) =21a(8) =30a(9) =68a(10) =73a(11) =169a(12) =176a(13) =345a(14) =823a(15) =1021a(16) =1191a(17) =2073a(18) =2755a(19) =10717a(20) =14673a(21) =16754a(22) =17606a(23) =81029a(24) =120851a(25) =167965a(26) =200408

External references