a(n) = ceiling(5^n/n).

Terms

a(0) =5a(1) =13a(2) =42a(3) =157a(4) =625a(5) =2605a(6) =11161a(7) =48829a(8) =217014a(9) =976563a(10) =4438921a(11) =20345053a(12) =93900241a(13) =435965402a(14) =2034505209a(15) =9536743165a(16) =44878791361a(17) =211927625869