Tic Tac No

Algorithm that will tie or beat you at tic-tac-toe:

1 2 3
4 5 6
7 8 9

The algorithm always goes first. It will always choose 5.
Choose a number to represent your turn.
The algorithm will choose your last turn * 2. If the result is >= 9, subtract 9.
If the algorithm chooses a place that is already taken, subtract 1 until it finds a place that isn't. If it hits 1, add 1 until it finds a free place.