Problem 963

Erdős Problem #963: declared status 'open'. Formalized: no. Let $f(n)$ be the maximal $k$ such that in any set $A\subset \mathbb{R}$ of size $n$ there is a subset $B\subseteq A$ of size $\lvert B\rvert\geq k$ which is dissociated that is, the sums $\sum_{b\in S}b$ are distinct for all $S\subseteq B$. Estimate $f(n)$ - in particular, is it true that$$f(n)\geq \lfloor \log_2 n\rfloor?$$ Prize: no. Tags: number theory.