Erdős problem 1102

There exists an infinite sequence $A = {a₁ < a₂ < …} ⊂ \mathsf{SF}$ where $\mathsf{SF} := \mathbb{N} \setminus \bigcup_{p} p^{2}\mathbb{N}$, i.e. the set of squarefree numbers. The set A has property Q and natural density 6 / π^2. Equivalently, (j / a_j) → 6/π^2 as j → ∞. -