CollapseProblem 428Is there a set A⊆NA\subseteq \mathbb{N}A⊆N such that, for infinitely many nnn, all of n−an-an−a are prime for all a∈Aa\in Aa∈A with 0<a<n0<a<n0<a<n and lim inf∣A∩[1,x]∣π(x)>0?\liminf\frac{\lvert A\cap [1,x]\rvert}{\pi(x)}>0?liminfπ(x)∣A∩[1,x]∣>0?Source: erdosproblems.com/428Number theoryPrimesWiki pageStatusOpenNo claim settles this problem.