检查一个数字在Python中是否可以表示为两个半质数的和

def is_prime(n):
    if n <= 1:
        return False
    if n <= 3:
        return True
    if n % 2 == 0 or n % 3 == 0:
        return False
    i = 5
    while i * i <= n:
        if n % i == 0 or n % (i + 2) == 0:
            return False
        i += 6
    return True

def generate_semiprimes(limit):
    semiprimes = set()
    for i in range(2, limit):
        if is_prime(i):
            for j in range(i, limit):
                if is_prime(j):
                    semiprime = i * j
                    if semiprime > limit:
                        break
                    semiprimes.add(semiprime)
    return semiprimes

def can_be_expressed_as_sum_of_semiprimes(n, semiprimes):
    for semiprime in semiprimes:
        if n - semiprime in semiprimes:
            return True
    return False

# 示例使用
limit = 1000
semiprimes = generate_semiprimes(limit)
number_to_check = 15
result = can_be_expressed_as_sum_of_semiprimes(number_to_check, semiprimes)
print(f"Can {number_to_check} be expressed as sum of two semiprimes? {result}")