natural numbcr的用法和樣例：
例句
- Today we are going to classify natural numbers by seeing how many divisors they have.
我們學習根據一個數約數的個數來對自然數進行分類。 - In this paper a new mutation operator is proposed, which is applied into chromosomes encoded with natural numbers.And the optimal mutation rate is studied.
針對自然數編碼的遺傳演算法，提出了一個新的變異規則，並研究了相應的最優變異率。
