Shown with a cast-on count of 2 stitches.  

• Rows 1, 3, 5, 7, 9, 11, 13, 15, and 17 (WS): Purl.
• Row 2: K1, yo, k1 (3 sts).
• Row 4: K1, yo, k1, yo, k1 (5 sts).
• Row 6: K1, yo, k1, yo, k1, yo, k1, yo, k1 (9 sts).
• Row 8: K1, yo, k2, yo, k1, yo, k1, yo, k1, yo, k2, yo, k1 (15 sts).
• Row 10: K1, yo, k1, ssk, k2tog, k1, yo, k1, yo, k1, ssk, k2tog, k1, yo, k1.
• Row 12: K1, yo, k1, yo, ssk, k2tog, yo, k1, yo, k1, yo, k1, yo, ssk, k2tog, yo, k1, yo, k1 (19 sts).
• Row 14: K1, yo, k2, ssk, k2tog, k1, yo, k1, yo, k1, yo, k1, yo, k1, ssk, k2tog, k2, yo, k1 (21 sts).
• Row 16: K1, yo, k2, ssk, k2tog, k3, yo, k1, yo, k3, ssk, k2tog, k2, yo, k1.