On a Certain Periodicity of Double-Indexed Poly-Bernoulli Numbers
摘要
As properties of poly-Bernoulli numbers, a number of formulas such as the duality formula, an explicit formula using the Stirling numbers of the second kind, and a periodicity for negative upper-index have been established. For the multi-indexed poly-Bernoulli numbers generalized by M. Kaneko and H. Tsumura, among such properties only the duality formula has been obtained. In this article, we focus on the double-indexed poly-Bernoulli numbers and show an explicit formula using the Stirling numbers of the second kind, along with a periodicity for the negative upper-index in this specific case. Furthermore, we define a variant of multi-indexed poly-Bernoulli numbers using the star-version of multiple polylogarithms and express this kind of double-indexed poly-Bernoulli numbers in terms of the original multi-indexed poly-Bernoulli numbers. In addition, we discuss the periodicity of it.