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

Abstract

George E. Andrews, Shalosh B. Ekhad, Doron Zeilberger, A Short Proof of Jacobi's Formula for the Number of Representations of an Integer as a Sum of Four Squares, The American Mathematical Monthly, Vol. 100, No. 3 (Mar., 1993), pp. 274-276