Pell's equation - Wikipedia

Pell number - Wikipedia

What integer solutions are there for the equation - tan (2π/n) = n ^ (1/(n-1))? - Quora

Art of Problem Solving

Square root of 6 - Wikipedia

Pell Equation - Wolfram Demonstrations Project

2023 Number Challenge: Pell's Equation with d=2023

Can any number theorists explain the patterns going on in this factorization? (Sorta relevant to cyclotomic polynomials.) : r/math

Pell Equation -- from Wolfram MathWorld

Continued fraction, Math Wiki