Cameron–Erdős conjecture on sum-free subsets

Let $[N]=\{1,\dots,N\}$. A subset $A$ of the integers is sum-free if there do not exist $x,y,z\in A$ such that $x+y=z$. Cameron–Erdős conjecture. The number of sum-free subsets of $[N]$ is $O(2^{N/2})$. This conjecture asks for the correct order of magnitude for the number of sum-free subsets of an initial interval of the positive integers. The paper states that the bound is proved, thereby confirming the conjecture.