Table[3^(1-n)(3n-2),{n,1,15}]

{1, 4/3, 7/9, 10/27, 13/81, 16/243, 19/729, 22/2187, 25/6561,
28/19683, 31/59049, 34/177147, 37/531441, 40/1594323, 43/4782969}