Hi I've got a problem on topology.
Let $\mathcal T$ be the class of subsets of positive integers consisting null set and all subsets of positive integers of the form $E_n =\{n,n+1,n+2,n+3,\dots\}$ with $n$ element of positive integers.
- Show that $\mathcal T$ is a topology on the set of positive integers.
- List the open sets containing the positive integer $G$.
Could you please help me?