Shown with a cast-on count of 1 stitch.  

• Row 0 (RS): Ctr dbl inc (3 sts).
• Rows 1, 3, 5, 7, 9, 11, 13, 15, and 17: Purl.
• Row 2: K1, (k1, yo, k1) in next st, knit (5 sts).
• Row 4: K1, (k1, yo, k1) in next st, knit (7 sts).
• Row 6: K1, (k1, yo, k1) in next st, knit (9 sts).
• Row 8: K1, (k1, yo, k1) in next st, knit (11 sts).
• Rows 10, 12, 14, 16, and 18: K1, (k1, yo, k1) in next st, knit (2 more sts).
• Row 19: BO 8 sts, purl (8 fewer sts).
• Repeat rows 10-19.