Integers k such that 2*5^k - 1 is prime.

Terms

a(0) =4a(1) =6a(2) =16a(3) =24a(4) =30a(5) =54a(6) =96a(7) =178a(8) =274a(9) =1332a(10) =2766a(11) =3060a(12) =4204a(13) =17736a(14) =190062a(15) =223536a(16) =260400a(17) =683080