even permutation

noun Mathematics.
  1. a permutation of a set of n elements, x1, x2, … xn, that leaves unchanged the product of all differences of the form (xixj), where i is less than j.

Origin of even permutation

First recorded in 1930–35
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018