宾果卡生成重复号码

我创建了一个简单的Bingo卡生成器，该生成器在n和n + 15之间生成4个数字，但是在测试它时，我注意到有时我会多次生成两次数字，尽管我放置了if语句，但我认为这会发现重复项并重新运行随机数函数

import random

ballCount = 75  # Max value of cell
gridWidth = 4
gridHeight = 5
numPerCard = 20  # Numbers generated per card
minimum = 1
maximum = 15


def generate_number(stored, small_num, big_num):
    random.seed(a=None, version=2)
    random_number = str(random.randint(small_num, big_num))
    if "| "+random_number+" |" in stored:
        generate_number(stored, small_num, big_num)
    return random_number


for row in range(gridHeight):
    string = ""
    for Number in range(gridWidth):
        number = generate_number(string, minimum, maximum)
        string += " | " + number
    string += " |"
    print(string)
    maximum += 15
    minimum += 15

输出错误的示例，其中两次打印23：

| 25 | 23 | 19 | 23 |
| 37 | 42 | 30 | 37 |
| 60 | 49 | 50 | 55 |
| 73 | 71 | 69 | 67 |