Shown with a cast-on count of 21 stitches.  

• Rows 1, 5, 7, and 9 (RS): K1, (k1, yo, k1) in next st, k1, *k3tog, yo, incL, k1, repeat from * to last 2 sts, (k1, yo, k1) in next st, k1 (multiple of 4 sts, plus 9).
• Rows 2 and 4: K1, purl to last st, k1.
• Row 3: K1, (k1, yo, k1) in next st, *k1, k3tog, yo, incL, repeat from * to last 3 sts, k1, (k1, yo, k1) in next st, k1 (multiple of 4 sts, plus 9).
• Rows 6, 8, and 10: K1, (p1, yo, p1) in next st, p1, *p3tog, yo, incLp, p1, repeat from * to last 2 sts, (p1, yo, p1) in next st, k1 (multiple of 4 sts, plus 9).
• Row 11: K1, (k1, yo, k1) in next st, k1, *k3tog, yo, incL, yo, k4tog, yo, incL, k1, repeat from * to last 2 sts, (k1, yo, k1) in next st, k1 (multiple of 8 sts, plus 9).
• Row 12: K1, (p1, yo, p1) in next st, purl to last 2 sts, (p1, yo, p1) in next st, k1 (4 more sts).