On the Asymptotic Density of $k$-tuples of Positive Integers Satisfying Arbitrary GCD Conditions
Chan Ieong Kuan
TL;DR
The paper tackles counting $k$-tuples $(n_1,\dots,n_k)$ with $n_i\le x$ that satisfy an arbitrary set of gcd-conditions. It develops a multivariable Dirichlet-series framework, decomposing conditions into prime components and applying Möbius convolution to extract the main term, with precise local factors shaping the Euler-product constant. A key admissibility criterion is established: $(\mathcal{Q},f)$ is admissible if and only if for every prime $p$ and every $T\in \mathcal{Q}$, $g_p(T)=\min\{v_i^{(p)}: i\in T\}$. For admissible sets, the count has the asymptotic form $A_{\mathcal{G}} x^k + O(x^{k-1}(\log x)^{k-1})$, where $A_{\mathcal{G}}$ is an explicit Euler product, generalizing known constants from Tóth’s results to arbitrary gcd-condition configurations. This provides a unified analytic toolkit for gcd-constrained tuple counts with potential broad applications in analytic number theory.
Abstract
We consider the problem of counting $k$-tuples of positive integers satisfying any arbitrary set of gcd conditions, where every integer is not larger than $x$. We first establish the conditions to guarantee the existence of such tuples, and then obtain asymptotic formulae for the count of such tuples with the help of a multivariable Dirichlet series. Part of this work can be viewed as a generalization of Tóth's work, where the conditions are pairwise.
