# More fun in 2015, Part 31

Consider a sequence $$\{ a_i \}$$ of distinct arbitrary natural numbers of length 2013.

Find the number of possible sequences of natural numbers of length $$2013$$ such that $$1\leq a_1 < a_2 < a_3 < \cdots < a_{2012}<a_{2013} \leq 2015$$

Bonus: Generalize this.

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