Smooshing together two patterns -- the yoga socks, with the Fancy Rib Stitch from:
http://www.ravelry.com/patterns/library/web-socks-fancy-r...

64 sts -- work fancy rib for 3.5” ending with row 4.

Arrange sts on needles so that there are 34 on needle 1 (instep), and 15 each on needles 2 and 3.

Begin ribbing rounds:

1) work fancy rib across instep, increase 6 sts evenly across needles 2 and 3.

work 4 rounds of ribbing, keeping needle 1 in pattern.