Shown with a cast-on count of 26 stitches.  

• Round 1: [K6, ctr dbl inc, k6] twice (30 sts).
• Rounds 2-4, 6-8, 10-12, 14-16, 18-20, 22-24, and 26-28: Knit.
• Round 5: [K7, ctr dbl inc, k7] twice (34 sts).
• Round 9: [K8, ctr dbl inc, k8] twice (38 sts).
• Round 13: [K9, ctr dbl inc, k9] twice (42 sts).
• Round 17: [K10, ctr dbl inc, k10] twice (46 sts).
• Round 21: [K11, ctr dbl inc, k11] twice (50 sts).
• Round 25: [K12, ctr dbl inc, k12] twice (54 sts).
• Round 29: [K13, ctr dbl inc, k13] twice (58 sts).