Nilasinwong, Lalita, and Kantaphon Kuhapatanakul. “Sums of Reciprocal Triangular Numbers”. Progress in Applied Science and Technology 10, no. 2 (October 8, 2020): 14–17. accessed October 14, 2026. https://ph02.tci-thaijo.org/index.php/past/article/view/242160.