sequence of sets with $\limsup A_n = \mathbb N$

Question

Find a sequence of one-point-sets $A_n = \{\ell_n\}$ with $\ell_n\in\mathbb N$ for all $n\in\mathbb N$, such that $$\limsup_{n\to\infty} A_n=\mathbb N$$

I know the definition of the $\limsup$ of a sequence of sets, $$\limsup_{n\to\infty} A_n = \bigcap_{n=1}^\infty \bigcup_{k=n}^\infty A_k$$ I know the sequence has to contain each number of $\mathbb N$ infinitely often, but I'm not able to find a suiting sequence.

Answer 1

$1,1,2,1,2,3,1,2,3,4,1,2,3,4,5,\ldots$