For each $\ n\in\mathbb{N},\ $ define the set $\ [n] := \{1,2,\ldots, n\}.\ $ Does there exist a real sequence $\ (a_n)_{n\in\mathbb{N}}\subset [0,1),\ $ such that for each $\ n\in\mathbb{N}\ $ there exists a bijection $\ f:[n]\to [n],\ $ such that $\ a_{f(k)} \in \left[ \frac{k-1}{n}, \frac{k}{n} \right)\ \forall\ k\in [n]\ ?$
In other words, can we construct a sequence $\ (a_n)_{n\in\mathbb{N}}\subset [0,1),\ $ such that for each $\ n\in\mathbb{N},\ \not\exists\ i,j,k\in [n]\ $ with $\ i\neq j\ $ and $\ a_i,a_j\in\left[ \frac{k-1}{n}, \frac{k}{n} \right)\ ?$
This is Steinhaus’s irregularity of distributions problem, and the answer is no: Berlekamp and Graham (1970) showed that such a sequence cannot be continued beyond $n = 17$.