Functiones et Approximatio Commentarii Mathematici

Fleck's congruence, associated magic squares and a zeta identity

Matthew C. Lettington

Abstract

Let the \emph{Fleck numbers}, $C_n(t,q)$, be defined such that $C_n(t,q)=\sum_{k\equiv q (mod n)}(-1)^k\binom{t}{k}.$ For prime $p$, Fleck obtained the result $C_p(t,q)\equiv 0 (mod p^{{\left \lfloor (t-1)/(p-1)\right \rfloor}}} )$, where $\lfloor.\rfloor$ denotes the usual floor function. This congruence was extended 64 years later by Weisman, in 1977, to include the case $n=p^\alpha$. In this paper we show that the Fleck numbers occur naturally when one considers a symmetric $n\times n$ matrix, $M$, and its inverse under matrix multiplication. More specifically, we take $M$ to be a symmetrically constructed $n\times n$ associated magic square of odd order, and then consider the reduced coefficients of the linear expansions of the entries of $M^t$ with $t\in \mathbb{Z}$. We also show that for any odd integer, $n=2m+1$, $n\geq 3$, there exist geometric polynomials in $m$ that are linked to the Fleck numbers via matrix algebra and $p$-adic interaction. These polynomials generate numbers that obey a reciprocal type of congruence to the one discovered by Fleck. As a by-product of our investigations we observe a new identity between values of the Zeta functions at even integers. Namely $\zeta{(2j)}=(-1)^{j+1}\left (\frac{j\pi^{2j}}{(2j+1)!}+\sum_{k=1}^{j-1}\frac{(-1)^k\pi^{2j-2k}}{(2j-2k+1)!}\zeta{(2k)}\right ).$ We conclude with examples of combinatorial congruences, Vandermonde type determinants and Number Walls that further highlight the symmetric relations that exist between the Fleck numbers and the geometric polynomials.

Article information

Source
Funct. Approx. Comment. Math., Volume 45, Number 2 (2011), 165-205.

Dates
First available in Project Euclid: 12 December 2011

https://projecteuclid.org/euclid.facm/1323705813

Digital Object Identifier
doi:10.7169/facm/1323705813

Mathematical Reviews number (MathSciNet)
MR2895154

Zentralblatt MATH identifier
1246.11043

Citation

Lettington, Matthew C. Fleck's congruence, associated magic squares and a zeta identity. Funct. Approx. Comment. Math. 45 (2011), no. 2, 165--205. doi:10.7169/facm/1323705813. https://projecteuclid.org/euclid.facm/1323705813