“…In particular, Corollary 3.2 in [19] points out that, when n = 2m, the set A consisting of (2m + 1) 2 points lying on 2m + 1 latitudes, each of them contains 2m + 1 equidistant points, solves the problem. In [10], the authors gave an analogous result, but each parallel circle contains an even number of points. To investigate the problem, the authors use the spherical coordinates…”