Shown with a cast-on count of 1 stitch.  

• Row 1 (WS): Ctr dbl inc (3 sts).
• Row 2: K1, ctr dbl inc, k1 (5 sts).
• Row 3: (P1, k1, p1) in next st, p3, (p1, k1, p1) in next st (9 sts).
• Row 4: K1, p1, k1, kfb, k1, kfb, k1, p1, k1 (11 sts).
• Row 5: P1, (p1, k1, p1) in next st, p1, p5, p1, (p1, k1, p1) in next st, p1 (15 sts).
• Row 6: K2, p1, k2, kfb, k3, kfb, k2, p1, k2 (17 sts).
• Row 7: P2, ctr dbl inc, p2, p7, p2, ctr dbl inc, p2 (21 sts).
• Row 8: K2, p3, k2, kfb, k5, kfb, k2, p3, k2 (23 sts).
• Row 9: P2, k1, ctr dbl inc, k1, p2, p9, p2, k1, ctr dbl inc, k1, p2 (27 sts).
• Row 10: K2, p5, k2, kfb, k7, kfb, k2, p5, k2 (29 sts).
• Row 11: P2, k5, p2, p11, p2, k5, p2.
• Row 12: K2, p2, ctr dbl inc, p2, k2, kfb, k9, kfb, k2, p2, ctr dbl inc, p2, k2 (35 sts).
• Row 13: P2, k2, p1, (p1, k1, p1) in next st, p1, k2, p2, p13, p2, k2, p1, (p1, k1, p1) in next st, p1, k2, p2 (39 sts).
• Row 14: K2, p2, k2, p1, k2, p2, k2, kfb, k11, kfb, k2, p2, k2, p1, k2, p2, k2 (41 sts).
• Row 15: P2, k2, p2, k1, p2, k2, p2, p15, p2, k2, p2, k1, p2, k2, p2.