Shown with a cast-on count of 34 stitches.  

• Row 1 (RS): K2, *k9, k3tog, [k1, yo] twice, k1, repeat from * to last 2 sts, k2.
• Rows 2, 4, 6, 8, 10, 12, 14, 16, and 18: K2, *p15, repeat from * to last 2 sts, k2.
• Row 3: K2, *k8, k3tog, k2, [yo, k1] twice, repeat from * to last 2 sts, k2.
• Row 5: K2, *k7, k3tog, k3, [yo, k1] twice, repeat from * to last 2 sts, k2.
• Row 7: K2, *k6, k3tog, k4, [yo, k1] twice, repeat from * to last 2 sts, k2.
• Row 9: K2, *k5, k3tog, k5, [yo, k1] twice, repeat from * to last 2 sts, k2.
• Row 11: K2, *k4, k3tog, k6, [yo, k1] twice, repeat from * to last 2 sts, k2.
• Row 13: K2, *k3, k3tog, k7, [yo, k1] twice, repeat from * to last 2 sts, k2.
• Row 15: K2, *k2, k3tog, k8, [yo, k1] twice, repeat from * to last 2 sts, k2.
• Row 17: K2, *k1, k3tog, k9, [yo, k1] twice, repeat from * to last 2 sts, k2.