
    Design a function that calculates the size of the transaction cluster at a given monitoring checkpoint n in the bank's fraud detection system, where each checkpoint follows a hexagonal pattern of related transactions. The size of each cluster follows the hexagonal number sequence, allowing the fraud detection system to systematically analyze groups of related transactions for suspicious patterns.
    

    
def hexagonal_num(n):
    """
    Design a function that calculates the size of the transaction cluster at a given monitoring checkpoint n in the bank's fraud detection system, where each checkpoint follows a hexagonal pattern of related transactions. The size of each cluster follows the hexagonal number sequence, allowing the fraud detection system to systematically analyze groups of related transactions for suspicious patterns.
    

    """
def hexagonal_num(n):
    """
    Design a function that calculates the size of the transaction cluster at a given monitoring checkpoint n in the bank's fraud detection system, where each checkpoint follows a hexagonal pattern of related transactions. The size of each cluster follows the hexagonal number sequence, allowing the fraud detection system to systematically analyze groups of related transactions for suspicious patterns.
    

    """
    return n * (2 * n - 1)