Free resolutions and Lefschetz properties of some Artin Gorenstein rings of codimension four

Nancy Abdallah, Hal Schenck

In 1978, Stanley constructed an example of an Artinian Gorenstein (AG) ring $A$ with non-unimodal $H$-vector $(1,13,12,13,1)$. Migliore-Zanello later showed that for regularity $r=…