The rectangular spiral or the $n_1 \times n_2 \times \cdots \times n_k$ Points Problem

A generalization of Rip\`a's square spiral solution for the $n \times n \times \cdots \times n$ Points Upper Bound Problem. Additionally, we provide a non-trivial lower bound for the $k$-dimensional $n_1 \times n_2 \times \cdots \times n_k$ Points Problem. In this way, we can build a range in which, with certainty, all the best possible solutions to the problem we are considering will fall. Finally, we give a few characteristic numerical examples in order to appreciate the fineness of the result arising from the particular approach we have chosen.
Comment: 9 pages, 3 figures. This is a short version of the original paper, published in NNTDM, for the reasons explained at page 9