Shown with a cast-on count of 3 stitches.  

• Row 1 (WS): P3.
• Row 2: K1, yo, k1, yo, k1 (5 sts).
• Row 3: Purl.
• Row 4: K1, yo, k1, (k1, yo, k1) in next st, k1, yo, k1 (9 sts).
• Row 5: P2tog, knit to last 2 sts, p2tog (7 sts).
• Row 6: K1, yo, k2, (k1, yo, k1) in next st, k2, yo, k1 (11 sts).
• Row 7: P2tog, knit to last 2 sts, p2tog (9 sts).
• Row 8: K1, yo, k3, (k1, yo, k1) in next st, k3, yo, k1 (13 sts).
• Row 9: P2tog, knit to last 2 sts, p2tog (11 sts).
• Row 10: K1, yo, k4, (k1, yo, k1) in next st, k4, yo, k1 (15 sts).
• Row 11: P2tog, knit to last 2 sts, p2tog (13 sts).
• Row 12: K1, yo, k5, (k1, yo, k1) in next st, k5, yo, k1 (17 sts).
• Row 13: P2tog, knit to last 2 sts, p2tog (15 sts).
• Row 14: K1, yo, k6, (k1, yo, k1) in next st, k6, yo, k1 (19 sts).
• Row 15: P2tog, knit to last 2 sts, p2tog (17 sts).
• Row 16: K1, yo, k7, (k1, yo, k1) in next st, k7, yo, k1 (21 sts).
• Row 17: P2tog, knit to last 2 sts, p2tog (19 sts).