KöMaL 2013 B4552

In this sentence, the number of numbers occurring once is $a_1$, the number of numbers occurring twice is $a_2$, ..., and the number of numbers occurring 2013 times is $a_{2013}$. Determine the values of $a_1, a_2, \ldots, a_{2013}$ such that the resulting statement is true. In how many different ways can that be done?