a(1) = 73, a(n) = prime(a(n-1)) - 4*a(n-1).

Terms

a(0) =73a(1) =75a(2) =79a(3) =85a(4) =99a(5) =127a(6) =201a(7) =425a(8) =1253a(9) =5199a(10) =29945a(11) =229823a(12) =2275065a(13) =28132841a(14) =423135497a(15) =7573775211a(16) =158441583469