Czechoslovak Mathematical Journal, online first, 17 pp.

# Density of solutions to quadratic congruences

## Neha Prabhu

#### Received December 31, 2015.   First published May 5, 2017.

Neha Prabhu, Indian Institute of Science Education and Research, Dr Homi Bhabha Rd, NCL Colony, Pashan, Pune, Maharashtra 411008, India, e-mail: neha.prabhu@students.iiserpune.ac.in

Abstract: A classical result in number theory is Dirichlet's theorem on the density of primes in an arithmetic progression. We prove a similar result for numbers with exactly $k$ prime factors for $k>1$. Building upon a proof by E. M. Wright in 1954, we compute the natural density of such numbers where each prime satisfies a congruence condition. As an application, we obtain the density of squarefree $n\leq x$ with $k$ prime factors such that a fixed quadratic equation has exactly $2^k$ solutions modulo $n$.

Keywords: Dirichlet's theorem; asymptotic density; primes in arithmetic progression; squarefree number

Classification (MSC 2010): 11D45, 11B25, 11N37

DOI: 10.21136/CMJ.2017.0712-15

Full text available as PDF.

References:
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