a(n) = 3^n + 5.

Terms

a(0) =6a(1) =8a(2) =14a(3) =32a(4) =86a(5) =248a(6) =734a(7) =2192a(8) =6566a(9) =19688a(10) =59054a(11) =177152a(12) =531446a(13) =1594328a(14) =4782974a(15) =14348912a(16) =43046726a(17) =129140168a(18) =387420494a(19) =1162261472a(20) =3486784406a(21) =10460353208a(22) =31381059614a(23) =94143178832a(24) =282429536486a(25) =847288609448