Prime subsequence of A077020 (also A001607).

Terms

a(0) =3a(1) =5a(2) =7a(3) =3a(4) =17a(5) =11a(6) =23a(7) =89a(8) =271a(9) =457a(10) =967a(11) =4049a(12) =181a(13) =8641a(14) =7193a(15) =2603047a(16) =68476319a(17) =335257649a(18) =5554901257a(19) =31797598073a(20) =23369856751