permutation) to compute the discrepancy from.
i1 : int
    The first line of the elementary permutation.
i2 : int
    The second line of the elementary permutation.
k : int
    The column of the elementary permutation.
disc : float
    Centered discrepancy of the design before permutation.

Returns
-------
discrepancy : float
    Centered discrepancy of the design after permutation.

References
----------
.. [1] Jin et al. "An efficient algorithm for constructing optimal design
   of computer experiments", Journal of Statistical Planning and
   Inference, 2005.

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