Foata D, Han G-N. The $(t,q)$-Analogs of Secant and Tangent Numbers. Electron. J. Combin. [Internet]. 2011May13 [cited 2026Mar.15];18(2):P7. Available from: https://www.combinatorics.org/ojs/index.php/eljc/article/view/v18i2p7