<human>:  Can you show me a Python function to count complete tree nodes.
<bot>: 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.