hi, i have a math problem

Term ......... . . Pattern

_________l__________________

...1 ............. 2

... 2 ............. 6

...3 ............. 18

...4 ............. 54

...5 ............. 162

so the pattern is start at 2 times 3 each time. but i need a expression

ex. n+5

N is the term, N and something else has to give me the pattern

please help me