Shown with a cast-on count of 7 stitches.  

• Row 1 (RS): K3, yo, k1, yo, k3 (9 sts).
• Rows 2, 4, 6, 12, and 14: Knit.
• Row 3: K3, yo, k1, yo, k1, yo, k1, yo, k3 (13 sts).
• Row 5: K3, yo, k3, yo, k1, yo, k3, yo, k3 (17 sts).
• Row 7: K3, yo, k5, yo, k1, yo, k5, yo, k3 (21 sts).
• Rows 8, 10, 16, and 18: K3, purl to last 3 sts, k3.
• Row 9: K3, yo, k7, yo, k1, yo, k7, yo, k3 (25 sts).
• Row 11: K3, yo, k9, yo, k1, yo, k9, yo, k3 (29 sts).
• Row 13: K3, yo, k11, yo, k1, yo, k11, yo, k3 (33 sts).
• Row 15: K3, yo, k13, yo, k1, yo, k13, yo, k3 (37 sts).
• Row 17: K3, yo, k15, yo, k1, yo, k15, yo, k3 (41 sts).