An Equidistribution Result for Differences Associated to Square Pyramidal Numbers II
Anji Dong, Katerina Saettone, Kendra Song, Alexandru Zaharescu
TL;DR
This work investigates the equidistribution of the sequence $a_n=|P_n-y_n^2|$, where $P_n=\sum_{i=1}^n i^2$, extending previous average results to arithmetic progressions and Dirichlet twists. The authors combine discrepancy bounds (Erd\H{o}s--Tur\'an), uniform distribution results (Kuipers--Niederreiter), and Euler--Maclaurin techniques to obtain a precise main term $A(b,q,x)=\frac{1}{5q\sqrt{3}}x^{3/2}$ with a power-saving error $O\left(\frac{x^{17/12}}{q^{2/3}}\right)$ for residue classes, along with twisted sum asymptotics $\sum_{n\le x} a_n\chi(n)$ and the corresponding Dirichlet-series pole structure. The paper further analyzes $b_n=\sum_{d|n}a_d$ and proves $\sum_{n\le x} b_n (1-n/x)=\frac{2\zeta(5/2)}{35\sqrt{3}}x^{7/2}+O_\delta(x^{41/12+\delta})$, using Perron-type methods and residue calculations. These results collectively advance equidistribution questions for square-pyramidal differences and illustrate a robust use of Dirichlet-series techniques in arithmetic-progression contexts.
Abstract
This paper presents some new results concerned with uniform distribution properties associated with the sequence $(a_n)_{n\in\mathbb{N}}$, which is defined as the distance from the $n$-th square pyramidal number to the closest square. We also extend the results to arithmetic progressions.
