# Isolated fraction

Algebra Level 3

If $$a_1,a_2,a_3,\ldots, a_n$$ are permutation of the set $$\{1,2,3,\ldots,n\}$$, what value can the following expression take?

$\large \prod_{1\leq i < j \leq n} \dfrac{a_j-a_i}{j-i}$

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