a(n) = ceiling(e^(n*(1+sqrt(5))/2)).

Terms

a(0) =6a(1) =26a(2) =129a(3) =647a(4) =3263a(5) =16453a(6) =82971a(7) =418433a(8) =2110227a(9) =10642223a(10) =53670491a(11) =270669172a(12) =1365029469a(13) =6884069717a(14) =34717503879a(15) =175086122783a(16) =882988319045