Least primes of the form k 4^n + (4^n-1)/3.

Terms

a(0) =2a(1) =5a(2) =5a(3) =149a(4) =853a(5) =2389a(6) =17749a(7) =70997a(8) =218453a(9) =2708821a(10) =3495253a(11) =13981013a(12) =39146837a(13) =492131669a(14) =626349397a(15) =27201459541a(16) =27201459541a(17) =297784399189a(18) =297784399189