Numbers k such that (61*10^k - 1)/3 is prime.

Terms

a(0) =3a(1) =17a(2) =18a(3) =30a(4) =78a(5) =98a(6) =371a(7) =947a(8) =1085a(9) =1560a(10) =1607a(11) =2145a(12) =4310a(13) =4637a(14) =16674a(15) =17148a(16) =25209a(17) =27929a(18) =33491a(19) =74189a(20) =124809a(21) =142446