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determine coprime factor base for a set of integers or ring elements
GCDFreeBasis(L: LIST of INT): LIST of INT
GCDFreeBasis(L: LIST of RINGELEM): LIST of RINGELEM 
This function returns a coprime factor base for a set of integers or ring
elements from a true GCD domain. A least cardinaility base can be obtained
by performing all possible GCD and exact division operations iteratively.
The factor base produced produced by these functions may not be of least
cardinality.
Given a set
N = [ N_1,...N_k ] we seek a factor base
G = [ G_1,...,G_s ] of
pairwise coprime values such that each
N_i is a product of powers of
the
G_j.
In general there many different such sets
G for a given set
N. Such sets are sometimes called a GCDfree bases for
N.
/**/ GCDFreeBasis([factorial(20), factorial(10)]);
[46189, 4, 14175]
/**/ use QQ[x,y];
/**/ GCDFreeBasis([x^2*y^4, x^3*y^6]);
