RND 5: (Sc next dc, dc next sc) around, sl st top beg sc, ch-1, turn.
RND 6: * (sc next dc, dc next sc) 3 times, (sc, dc) next 2 sts, * rep bet ** around, sl st top beg sc, ch-1, turn. (50 sts)
RND 7: * (sc next dc, dc next sc) 4 times, (sc, dc) next 2 sts), * rep bet ** around, sl st top beg sc, ch-1, turn. (60 sts)
RND 8: Rep rnd 5.
RND 9: Rep rnd 4. (80 sts)
RND 10: Rep rnd 5.
RND 11: Rep rnd 6. (100 sts)
RND 12-13: Rep rnd 5.
RND 14: Rep rnd 7. (120 sts)
RND 15-16: Rep rnd 5.
RND 17: Rep rnd 7. (144 sts)
RND 18-21: Rep rnd 5. At the end of rnd 21 fasten off.