Shown with a cast-on count of 39 stitches.  

• Row 1 (RS): K2, *p3, k2tog, yo, k1, yo, ssk, p3, k1, repeat from * to last st, k1.
• Rows 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20: Purl.
• Row 3: K2, *p2, k2tog, yo, p1, k1, p1, yo, ssk, p2, k1, repeat from * to last st, k1.
• Row 5: K2, *p1, k2tog, yo, p2, k1, p2, yo, ssk, p1, k1, repeat from * to last st, k1.
• Row 7: K2, *k2tog, yo, p3, k1, p3, yo, ssk, k1, repeat from * to last st, k1.
• Row 9: K1, k2tog, yo, *p4, k1, p4, yo, sl2-k1-p2sso, yo, repeat from * to last 12 sts, p4, k1, p4, yo, ssk, k1.
• Row 11: K2, *yo, ssk, p3, k1, p3, k2tog, yo, k1, repeat from * to last st, k1.
• Row 13: K2, *p1, yo, ssk, p2, k1, p2, k2tog, yo, p1, k1, repeat from * to last st, k1.
• Row 15: K2, *p2, yo, ssk, p1, k1, p1, k2tog, yo, p2, k1, repeat from * to last st, k1.
• Row 17: K2, *p3, yo, ssk, k1, k2tog, yo, p3, k1, repeat from * to last st, k1.
• Row 19: K2, *p4, yo, sl2-k1-p2sso, yo, p4, k1, repeat from * to last st, k1.
• Repeat rows 1-20.