A remark on a result of Helfgott, Roton and Naslund
  Let $F(X)= \prod_{i=1}^k(a_iX+b_i)$ be a polynomial with $a_i, b_i$ being integers. Suppose the discriminant of $F$ is non-zero and $F$ is admissible. Given any natural number $N$, let $S(F,N)$ denotes those integers less than or equal to $N$ such that $F(n)$ has no prime factors less than or equal to $N^{1/(4k+1)}.$ Let $L$ be a translation invariant linear equation in $3$ variables. Then any $A\subset S(F, N)$ with $\delta_F(N): = \frac{|A|}{|S(F,N)|} \gg_{\epsilon, F, L}\frac{1}{(\log \log N)^{1-\epsilon}}$ contains a non-trivial solution of $L$ provided $N$ is sufficiently large. 
Gyan Prakash
math.NT