English

The density of primes dividing a particular non-linear recurrence sequence

Number Theory 2018-01-22 v2

Abstract

Define the sequence {bn}\{b_n\} by b0=1,b1=1,b2=2,b3=1b_0=1,b_1=1, b_2=2,b_3=1, and b_n=\begin{cases} \frac{b_{n-1}b_{n-3}-b_{n-2}^2}{b_{n-4}}&\textrm{if}~ n\not\equiv 0\pmod 3, \frac{b_{n-1}b_{n-3}-3b_{n-2}^2}{b_{n-4}}&\textrm{if}~ n\equiv 0\pmod 3. We relate this sequence {bn}\{b_n\} to the coordinates of points on the elliptic curve E:y2+y=x33x+4E:y^2+y=x^3-3x+4. We use Galois representations attached to EE to prove that the density of primes dividing a term in this sequence is equal to 179336\frac{179}{336}. Furthermore, we describe an infinite family of elliptic curves whose Galois images match that of EE.

Keywords

Cite

@article{arxiv.1508.02464,
  title  = {The density of primes dividing a particular non-linear recurrence sequence},
  author = {Alexi Block Gorman and Tyler Genao and Heesu Hwang and Noam Kantor and Sarah Parsons and Jeremy Rouse},
  journal= {arXiv preprint arXiv:1508.02464},
  year   = {2018}
}

Comments

23 pages, with an appendix giving an alternative definition of the sequence

R2 v1 2026-06-22T10:30:41.267Z