Primes of the form 2*k!! + 1.

Terms

a(0) =3a(1) =3a(2) =5a(3) =7a(4) =17a(5) =31a(6) =97a(7) =211a(8) =769a(9) =7681a(10) =270271a(11) =68918851a(12) =371589121