RKR1-16 is R.J. Le Roy's program for applying the first-order semiclassical Rydberg-Klein-Rees procedure to calculate a pointwise potential energy function for a diatomic molecule from a knowlege of its spectroscopic constants. A full description of the most recent version of this code has been published in J. Quant. Spectrosc. Radiat. Transfer 186, 158 (2016), which is available at http://dx.doi.org/10.1016/j.jqsrt.2016.03.030, while the corresponding source code and detailed Program Manual are available as Supplementary "Application" files at that www link. All future citations regarding use of this code should refer to this Journal Article.