Lean-Workbook Syntax 48310: A telescoping product for differences of powers

For integers $x,y$ and natural $n$, $(x-y)\prod_{k=0}^{n-1}(x^{2^k}+y^{2^k})=x^{2^n}-y^{2^n}$.

Source: Lean-Workbook row lean_workbook_plus_48310 (Apache-2.0), original record. This corrected declaration replaces the obsolete finite sum/product binder in with ∈ and restores required imports or namespaces. Ranges, casts, quantifiers, and mathematical expressions are preserved.