Numbers k such that (10^k - 97)/3 is prime.

Terms

a(0) =4a(1) =5a(2) =7a(3) =13a(4) =16a(5) =22a(6) =30a(7) =56a(8) =78a(9) =80a(10) =90a(11) =194a(12) =316a(13) =1796a(14) =2004a(15) =3856a(16) =5226a(17) =6737a(18) =10841a(19) =43638a(20) =50467a(21) =85666