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In mathematics, in the area of combinatorics, a ''q''-Pochhammer symbol, also called a ''q''-shifted factorial, is a ''q''-analog of the common Pochhammer symbol. It is defined as : with : by definition. The ''q''-Pochhammer symbol is a major building block in the construction of ''q''-analogs; for instance, in the theory of basic hypergeometric series, it plays the role that the ordinary Pochhammer symbol plays in the theory of generalized hypergeometric series. Unlike the ordinary Pochhammer symbol, the ''q''-Pochhammer symbol can be extended to an infinite product: : This is an analytic function of ''q'' in the interior of the unit disk, and can also be considered as a formal power series in ''q''. The special case : is known as Euler's function, and is important in combinatorics, number theory, and the theory of modular forms. ==Identities== The finite product can be expressed in terms of the infinite product: : which extends the definition to negative integers ''n''. Thus, for nonnegative ''n'', one has : and : The ''q''-Pochhammer symbol is the subject of a number of ''q''-series identities, particularly the infinite series expansions : and :, which are both special cases of the q-binomial theorem: : 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Q-Pochhammer symbol」の詳細全文を読む スポンサード リンク
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