Powers of 9: a(n) = 9^n.

Terms

a(0) =1a(1) =9a(2) =81a(3) =729a(4) =6561a(5) =59049a(6) =531441a(7) =4782969a(8) =43046721a(9) =387420489a(10) =3486784401a(11) =31381059609a(12) =282429536481