摘要：
Let S be a set of $n$ objects; then the binomial coefficient $(^n_k)$ is the number of $k$-elements subsets of $S$. Thus $\sum_{k=0}^n(^n_k)$ is the n 阅读全文
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摘要：
Let S be a set of $n$ objects; then the binomial coefficient $(^n_k)$ is the number of $k$-elements subsets of $S$. Thus $\sum_{k=0}^n(^n_k)$ is the n 阅读全文
摘要：
The power set of a set A is the collection of all subsets of A. When working with a finite set with n elements, one question that we might ask is, “Ho 阅读全文
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