In this paper,summation formulas of products involving odd-even index chebyshev polynomials of the second are given by using primary methods. 利用初等方法给出了一类包含奇下标第二类契贝谢夫多项式乘积和与一类包含偶下标第二类契贝谢夫多项式乘积和的求和公式。
In this peper necessary and sufficient conditions for the semidirect products and wreath products of two scmigroup are given. 给出了两个半群的半直积和圈积为左群的充分必要条件以及半直积的结构。
