Shown with a cast-on count of 1 stitch.  

• Row 1 (RS): Yo, k1, yo (3 sts).
• Row 2: P3.
• Row 3: Yo, k3, yo (5 sts).
• Row 4: P5.
• Row 5: Yo, k2tog, yo, k1, yo, ssk, yo (7 sts).
• Row 6: P7.
• Row 7: Yo, k7, yo (9 sts).
• Row 8: P9.
• Row 9: Yo, k1, yo, k3tog, yo, k1, yo, sl1-k2tog-psso, yo, k1, yo (11 sts).
• Row 10: P11.
• Row 11: Yo, k11, yo (13 sts).
• Row 12: P13.
• Row 13: Yo, k2tog, yo, sl1-k2tog-psso, yo, k1, yo, k1, yo, k1, yo, k3tog, yo, ssk, yo (15 sts).
• Row 14: P15.
• Row 15: Yo, k15, yo (17 sts).
• Row 16: P17.
• Row 17: Yo, k2tog, yo, k2tog, yo, k2tog, yo, k2tog, yo, k1, yo, ssk, yo, ssk, yo, ssk, yo, ssk, yo (19 sts).
• Row 18: P19.
• Row 19: Yo, p19, yo (21 sts).
• Row 20: P21.