Numbers k such that 4*10^k + 6*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

A099005

Numbers k such that 4*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) =4a(4) =6a(5) =7a(6) =8a(7) =12a(8) =23a(9) =59a(10) =75a(11) =144a(12) =204a(13) =268a(14) =760a(15) =1216a(16) =1430a(17) =1506a(18) =1509a(19) =2804a(20) =2924a(21) =3201a(22) =3305a(23) =5753a(24) =9268a(25) =11279a(26) =19677a(27) =23414a(28) =28627a(29) =31362

External references