Human: count complete tree nodes. Assistant: 
Here is a Python function to count complete tree nodes

import math

def count_complete_tree_nodes(n):
        """Count the number of nodes in a complete tree of height n."""
        if n == 0:
            return 1
        return 1 + 2 * count_complete_tree_nodes(n - 1)

# Enter the number of levels
n = 3

# Calling the function
print((count_complete_tree_nodes(n)))

#Example Output
# 15

#Remember to inspect code for bugs.