Cast on a multiples of 3 sts, +1 and 2-row repeat.
Row 1 (Right side): Purl 1, *Knit through the back loop of the second stitch on the left needle, then knit through the front of the first stitch, and drop them both from the needle at the same time, purl 1; Repeat from * to end.
Row 2: Knit 1, * Purl the second stitch on the left needle, then purl the first stitch, and drop them both from the needle at the same time, knit 1; Repeat from * to end.