2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/123970In this note we obtain defining equations of modular curves $X_0(2^{2n})$. The key ingredient is a recursive formula for certain generators of the function fields on $X_0(2^{2n})$.6 pagesNumber Theory11F03; 11G05; 11G18; 11G30Defining equations of $X_0(2^{2n})$text