Smallest prime >= 5^n.

Terms

a(0) =2a(1) =5a(2) =29a(3) =127a(4) =631a(5) =3137a(6) =15629a(7) =78137a(8) =390647a(9) =1953151a(10) =9765629a(11) =48828139a(12) =244140683a(13) =1220703131a(14) =6103515637a(15) =30517578167a(16) =152587890649a(17) =762939453127