Y Hu, M Le - Periodica Mathematica Hungarica, 2023 - Springer
Let D be a fixed nonsquare positive integer, and let {un} n= 1∞ denote the X-coordinates of
the Pell equation u 2-D v 2= 1. Further, for any fixed nonnegative integer r, let S (D, r)={n| n∈ …