A Short Proof of Jacobi's Formula for the Number of Representations of an Integer as a Sum of Four Squares

2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/152802A short and elementary proof, and a finite-form generalization, are given of Jacobi's formula for the number of ways of writing an integer as a sum of four squares (that implies Lagrange's famous 1777 theorem.)Plain TeXCombinatoricsA Short Proof of Jacobi's Formula for the Number of Representations of an Integer as a Sum of Four Squarestext