I am trying to find a function corresponding to the following sequence:
3, 9, 21, 45, 93, 189, ...
I am measuring the number of recursive calls of a function where I call the function three times in every iteration, so I would expect it to be an exponential function.
If it is, how could I proceed to find it ?
Hint: Note that $9-3=6,$ $21-9=12,$ $45-21=24,$ $93-45=48,$ and so on. Does that get you there?