Erdös–Straus conjecture (m = 4)
Prove that for every integer n ≥ 2 there exist integers x, y, and z such that 4/n = 1/x + 1/y + 1/z.
References
Two well known conjectures by Erdös-Straus and Sierpinski state that the diophantine equation m/ n =1/ x+1/ y+1/ z has integer solutions x, y,zfor every integer n ≥ 2and m = 4 (Erdös-Straus) or m = 5 (Sierpinski). There is an impressive body of evidence for the validity of both conjectures, see e.g. [1,2,3,5], but no valid proof.
                — Unique polynomial solution of $m/n=1/x+1/y+1/z$ for $n \equiv b {\rm mod}\, a$ if $(a,m)=1$
                
                (2404.01307 - Schuh, 3 Mar 2024) in Section I (Introduction)