We prove that the largest Q2-free family of subsets of [n] which
contains sets of at most three different sizes has at most $(3 + 2\sqrt {3})N/3
- o(N) \approx 2.1547N + o(N)members,whereN = {n \choose {\lfloor n/2
\rfloor}}.Thisimprovesanearlierboundof2.207N + o(N)$ by Axenovich,
Manske, and Martin.