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N-1st Betti multidegrees of monomial ideals using Mayer-Vietoris trees
MayerVietorisTreeN1(I:MONOMIAL IDEAL):INT
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This function returns the list of multidegrees M such that the N-1st
Betti number of a monomial ideal I at multidegree M is not zero.
It is computed via a version of its Mayer-Vietoris tree.
The length of this list is the number of irreducible components of I,
the number of maximal standard monomials, and the number of generators
of its Alexander Dual.
Use Q[x,y,z];
I := Ideal(x, y, z)^2;
MayerVietorisTreeN1(I);
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[x^2yz, xy^2z, xyz^2]
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