Hey,

I am considering the set $\displaystyle \mathcal{P}_{k}(\mathbb{N})$ which is the set of subsets of $\displaystyle \mathbb{N}$ with $\displaystyle k$ elements.

I want to find a injective function $\displaystyle \phi_{k}:\mathcal{P}_{k}(\mathbb{N}) \rightarrow \mathbb{N}^{k}$.

Suggestions ppreciated.