a(1) = 12, a(n) = prime(a(n-1)) - 2a(n-1).

Terms

a(0) =12a(1) =13a(2) =15a(3) =17a(4) =25a(5) =47a(6) =117a(7) =409a(8) =1985a(9) =13269a(10) =116555a(11) =1301043a(12) =17911307a(13) =296651169a(14) =5792367991a(15) =131137897895