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arXiv 1604.07089math.NTmath.CO
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由素数幂可除的二项式系数计数产生的一个显式generating function

An explicit generating function arising in counting binomial coefficients divisible by powers of primes

Lukas Spiegelhofer, Michael Wallner

摘要:

对于素数$p$和非负整数$j$和$n$,令$\vartheta_p(j,n)$是帕斯卡三角形的第$n$行中可被$p^j$整除的条目数。此外,对于$\{0,\ldots,p-1\}$中的有限序列$w=(w_{r-1}\cdots w_0)\neq (0,\ldots,0)$,我们用$\lvert n\rvert_w$表示$w$作为$n$的基- $p$扩展$n=(n_{μ-1}\cdots n_0)_p$的因子(连续子序列)出现的次数.从Barat和Grabner的工作(二项式系数的数字函数和分布,J. London Math. Soc.(2)64(3),2001)得出,$\vartheta_p(j,n)/\vartheta_p(0,n)$由变量$X_w$中的多项式$P_j$给出,其中$w$是$\{0,\ldots,p-1\}$中的某些有限字,并且每个变量$X_w$被设置为$\lvert n\rvert_w$。这后来由Rowland(The number of nonzero二项式系数modulo $p^α$,J. Comb. Number Theory 3(1),2011)明确表示,独立于Barat和Grabner的工作,并且Rowland描述并实现了计算这些多项式$P_j$的算法。本文用生成函数表示$P_j$的系数,并证明了这些生成函数可以通过递推关系显式确定。此外,我们证明了$P_j$是唯一确定的,我们注意到,我们的主要定理的证明也提供了一个新的证明,它的存在性。除了提供深入了解的多项式$P_j$的结构,我们的结果使我们能够计算它们在一个非常有效的方式。

英文摘要:

For a prime $p$ and nonnegative integers $j$ and $n$ let $\vartheta_p(j,n)$ be the number of entries in the $n$-th row of Pascal's triangle that are exactly divisible by $p^j$. Moreover, for a finite sequence $w=(w_{r-1}\cdots w_0)\neq (0,\ldots,0)$ in $\{0,\ldots,p-1\}$ we denote by $\lvert n\rvert_w$ the number of times that $w$ appears as a factor (contiguous subsequence) of the base-$p$ expansion $n=(n_{μ-1}\cdots n_0)_p$ of $n$. It follows from the work of Barat and Grabner (Digital functions and distribution of binomial coefficients, J. London Math. Soc. (2) 64(3), 2001), that $\vartheta_p(j,n)/\vartheta_p(0,n)$ is given by a polynomial $P_j$ in the variables $X_w$, where $w$ are certain finite words in $\{0,\ldots,p-1\}$, and each variable $X_w$ is set to $\lvert n\rvert_w$. This was later made explicit by Rowland (The number of nonzero binomial coefficients modulo $p^α$, J. Comb. Number Theory 3(1), 2011), independently from Barat and Grabner's work, and Rowland described and implemented an algorithm computing these polynomials $P_j$. In this paper, we express the coefficients of $P_j$ using generating functions, and we prove that these generating functions can be determined explicitly by means of a recurrence relation. Moreover, we prove that $P_j$ is uniquely determined, and we note that the proof of our main theorem also provides a new proof of its existence. Besides providing insight into the structure of the polynomials $P_j$, our results allow us to compute them in a very efficient way.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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