
    Design a function that determines the number of possible ways to organize user attributes into meaningful friend recommendation groups, where each attribute can only belong to one group and all attributes must be used. Given n social attributes (such as interests, hobbies, or interaction patterns), calculate how many different ways these attributes can be clustered to create distinct recommendation strategies.
    

    
def bell_number(n):
    """
    Design a function that determines the number of possible ways to organize user attributes into meaningful friend recommendation groups, where each attribute can only belong to one group and all attributes must be used. Given n social attributes (such as interests, hobbies, or interaction patterns), calculate how many different ways these attributes can be clustered to create distinct recommendation strategies.
    

    """
def bell_number(n):
    """
    Design a function that determines the number of possible ways to organize user attributes into meaningful friend recommendation groups, where each attribute can only belong to one group and all attributes must be used. Given n social attributes (such as interests, hobbies, or interaction patterns), calculate how many different ways these attributes can be clustered to create distinct recommendation strategies.
    

    """
    bell = [[0 for i in range(n + 1)] for j in range(n + 1)]
    bell[0][0] = 1
    for i in range(1, n + 1):
        bell[i][0] = bell[i - 1][i - 1]
        for j in range(1, i + 1):
            bell[i][j] = bell[i - 1][j - 1] + bell[i][j - 1]
    return bell[n][0]