a(n) = 3^n + n^3.

Terms

a(0) =1a(1) =4a(2) =17a(3) =54a(4) =145a(5) =368a(6) =945a(7) =2530a(8) =7073a(9) =20412a(10) =60049a(11) =178478a(12) =533169a(13) =1596520a(14) =4785713a(15) =14352282a(16) =43050817a(17) =129145076a(18) =387426321a(19) =1162268326a(20) =3486792401a(21) =10460362464a(22) =31381070257a(23) =94143190994a(24) =282429550305a(25) =847288625068