Skip to main content
2 of 2
added 224 characters in body

Not exactly the most frequent mathematical object in the literature, however, here is an interesting instance where this quantity occurs.

Take the the statistical average of $\prod_{i,j} a_{ij}$ over a special unitary $n\times n$ matrix $A$ chosen uniformly at random (i.e., Haar-distributed). Showing this expectation is nonzero for $n$ even is equivalent to the Alon-Tarsi conjecture. For an attempt at explaining why (I think) this conjecture is important, see my answer at this MO post:

What are the current breakthroughs of Geometric Complexity Theory?