What is the number of rows in a truth table for a well-formed formula that has n different statement letters?

Explanation

For a single statement letter, you have two possibilities T or F

For a two statement letters formula, you have two possibilities for each one, and the permutation = 2 * 2 = 4, or 2²

For 3 letters, permutation = 2 * 2 * 2 = 2³

So for n letters formula, it will be 2ⁿ

Have a look into the below binary tree