Triple double decrease: K2, s2kp, [insert LH ndl in back of 2nd st on RH ndl, slip first 2 sts off RH ndl, bring right ndl tip to front and pick up free st, sl 1 from LH ndl, k1, pass 2nd and 3rd sts on RH ndl over first st] two times.
Shown with a cast-on count of 13 stitches.