A Formal Proof of the Irrationality of $ζ(3)$ in Lean 4

Abstract: We present a formal proof of the irrationality of $\zeta(3)$ in Lean 4, based on Beuker's method. In addition, we contribute to the Mathlib library by formalizing shifted Legendre polynomials and several key results in analytic number theory, addressing gaps in Lean's analytical capabilities. As part of the Prime Number Theorem project in Lean 4, we formalize the asymptotic behavior of the prime counting function, which is essential for proving the irrationality of $\zeta(3)$.