Knitted in a multiple of 2 sts and 4-row repeat.
Row 1 (Wrong side): K2, * yf sl 1 yo, k1; repeat from * to end.
Row 2 (Right side): K1, * brk 1, k1; repeat from * to last st, k1.
Row 3: K1, * yf sl 1 yo, k1; repeat from * to last st, k1.
Row 4: K2, * brk 1, k1; repeat from * to end.
YF SL 1 YO: Bring working yarn to front under the needle, slip 1 stitch purlwise, bring working yarn over top of needle to the back. This produces a yarn over that crosses over the slipped stitch.
BRK 1: Knit the stitch that was slipped in the previous row together with its yarn over. Because the yarn over wasn't counted as a separate stitch on the previous row, no real decrease is made.