Shown with a cast-on count of 2 stitches.  

• Row 1 (RS): K2.
• Rows 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, and 40: Purl.
• Row 3: K1, yo, k1 (3 sts).
• Row 5: K1, yo, p1, yo, k1 (5 sts).
• Row 7: K2, yo, p1, yo, k2 (7 sts).
• Row 9: K2, yo, k1, yo, p1, yo, k1, yo, k2 (11 sts).
• Row 11: K3, yo, k2, yo, p1, yo, k2, yo, k3 (15 sts).
• Row 13: Ssk, k2, yo, ssk, yo, k1, yo, p1, yo, k1, yo, k2tog, yo, k2, k2tog (17 sts).
• Row 15: Ssk, k2, yo, ssk, yo, k2, yo, p1, yo, k2, yo, k2tog, yo, k2, k2tog (19 sts).
• Row 17: Ssk, k2, yo, ssk, yo, ssk, yo, k1, yo, p1, yo, k1, yo, k2tog, yo, k2tog, yo, k2, k2tog (21 sts).
• Row 19: Ssk, k2, yo, ssk, yo, ssk, yo, ssk, yo, p1, yo, k2tog, yo, k2tog, yo, k2tog, yo, k2, k2tog.
• Row 21: Ssk, k2, yo, ssk, yo, ssk, yo, ssk, k1, k2tog, yo, k2tog, yo, k2tog, yo, k2, k2tog (19 sts).
• Row 23: Ssk, k2, yo, ssk, yo, ssk, yo, sl2-k1-p2sso, yo, k2tog, yo, k2tog, yo, k2, k2tog (17 sts).
• Row 25: Ssk, k2, yo, ssk, yo, ssk, k1, k2tog, yo, k2tog, yo, k2, k2tog (15 sts).
• Row 27: Ssk, k2, yo, ssk, yo, sl2-k1-p2sso, yo, k2tog, yo, k2, k2tog (13 sts).
• Row 29: Ssk, k2, yo, ssk, k1, k2tog, yo, k2, k2tog (11 sts).
• Row 31: Ssk, k2, yo, sl2-k1-p2sso, yo, k2, k2tog (9 sts).
• Row 33: Ssk, k5, k2tog (7 sts).
• Row 35: Ssk, k3, k2tog (5 sts).
• Row 37: Ssk, k1, k2tog (3 sts).
• Row 39: Sl2-k1-p2sso (1 st).