Shown with a cast-on count of 12 stitches.  

• Row 1 (RS): K5, yo, k1, yo, k1, yo, k5 (15 sts).
• Row 2: P15.
• Row 3: K5, yo, k1, yo, k1, yo, k8 (18 sts).
• Row 4: P18.
• Row 5: K5, yo, k1, yo, k1, yo, k11 (21 sts).
• Row 6: P21.
• Row 7: K5, yo, k1, yo, k1, yo, k14 (24 sts).
• Row 8: P24.
• Row 9: K5, yo, k1, yo, k1, yo, k17 (27 sts).