This is driving me crazy. I've looked every where on-line for this pattern and can't find it. I could probably figure out how to make it myself, but if there's instructions on how to make it already out "there", then why not go with that. It's called a Wave Border Pillowcase and is made with three different fabrics to coordinate with your quilt. The main part of the pillowcase is one fabric, and the hemmed border is curvy and made with the remaining two fabrics, one on the inside and one on the outside.
Wave Border Pillowcase