In the Tower of Hanoi problem with 3 rods (1, 2 & 3), the goal is to move a tower of disks from rod #1 to rod #2. You can move disks only one by one, on the rods. You can't put a disk on a smaller one.
At the beginning, all disks are on rod #1, biggest at the bottom, smallest at the top.
Give the number of moves necessary to solve the problem.