On the Betti numbers of some semigroup rings
arXiv:1111.1433
Abstract
For any numerical semigroup , there are infinitely many numerical symmetric semigroups such that is their half. We are studying the Betti numbers of the numerical semigroup ring when is a 3-generated numerical semigroup or telescopic. We also consider 4-generated symmetric semigroups and the so called 4-irreducible numerical semigroups.