On solution-free sets of integers
  Given a linear equation $\mathcal{L}$, a set $A \subseteq [n]$ is $\mathcal{L}$-free if $A$ does not contain any `non-trivial' solutions to $\mathcal{L}$. In this paper we consider the following three general questions:   (i) What is the size of the largest $\mathcal{L}$-free subset of $[n]$?   (ii) How many $\mathcal{L}$-free subsets of $[n]$ are there?   (iii) How many maximal $\mathcal{L}$-free subsets of $[n]$ are there?   We completely resolve (i) in the case when $\mathcal{L}$ is the equation $px+qy=z$ for fixed $p,q\in \mathbb N$ where $p\geq 2$. Further, up to a multiplicative constant, we answer (ii) for a wide class of such equations $\mathcal{L}$, thereby refining a special case of a result of Green. We also give various bounds on the number of maximal $\mathcal{L}$-free subsets of $[n]$ for three-variable homogeneous linear equations $\mathcal{L}$. For this, we make use of container and removal lemmas of Green. 
Robert Hancock and Andrew Treglown
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