Skip elements in the Sobol sequence.
a 1 x 1 matrix of floating point integers, the number of elements to discard
a 1 x 1 matrix of floating point integers, the number of dimensions
a dim_num x 1 matrix of floating point integers, the numerators of the last vector generated
a 1 x 1 matrix of floating point integers, the index of the element in the sequence
The only difference with lowdisc_sobolnext is that we do not generate the vector quasi.
This routine is designed to be used with the lowdisc_sobolnext() and lowdisc_sobolstart() functions.