sage: R.<X, Y, Z> = QQ[]
sage: I = R.ideal([X^2*Y^3, X*Z])
sage: I.hilbert_polynomial()
-t - 5

The Hilbert polynomial, by definition, has to take non-negative integer values at all sufficiently large integers t, so this computation can't possibly be right. The correct answer is t + 5, which is what one gets with the algorithm='singular' option.

Inspecting the code, it looks like the denominator of the Hilbert series is getting normalised wrongly in some cases.

Component: commutative algebra

Author: Frédéric Chapoton, Kwankyu Lee

Branch/Commit: 98f118d

Reviewer: Kwankyu Lee, Frédéric Chapoton

Issue created by migration from https://trac.sagemath.org/ticket/33597