Optimal Farey sequence for the Congruence subgroup $Γ_0(2^{n})$
Abstract
We prove that $Γ_0(2^n)$ ($n\ge2$) has a Farey sequence $\{e_i\}$ such that $e_i \le 2^{n-1}$ for all $e_i$. The above upper bound is optimal, and there exists a unique $j$ such that $e_j= 2^{n-1} $. For each $e_i$, there exists a unique $a_i$ such that $\{ a_i/e_i\}\cup \{\infty\}$ is the set of ideal vertices of a fundamental domain of $Γ_0(2^n)$ whose side-pairings give a set of independent generators of $Γ_0(2^n)$.
Fields of Study & Subjects
Analytic Number Theory Research
Rings
Modules
and Algebras
Algebraic Geometry and Number Theory
Publication details
- Journal / source
- arXiv (Cornell University)
- Publication date
- 4 January 2026
- Document type
- Preprint