Lagrange and the four-square theorem - Archive ouverte HAL

In this article we will first provide an overview of Lagrange’s arithmetic work, written between 1768 and 1777. We then focus on the proof of the four-square theorem published in 1772, and shed light on the context of its implementation by relying on other memoirs by Lagrange and Leonhard Euler. By means of this analysis, our goal is to give a concrete vision of the arithmetic, algebraic and analytical methods and tools used by Lagrange in number theory and place his arithmetic practice in the context of the second half of the eighteenth century.

Pourchet's theorem in action: decomposing univariate nonnegative polynomials as sums of five squares

Chit-chat on Lagrange's four-square theorem

Publications - DQMP

Lagrange's Four-Square Theorem, PDF, Number Theory

Moment maps and cohomology of non-reductive quotients

Lagrange's Four-Square Theorem Seen Using Polygons and Lines - Wolfram Demonstrations Project

PDF) SAMPTA'09, International Conference on SAMPling Theory and Applications

Analyzing teachers' classroom experiences of teaching with dynamic geometry environments: Comparing and Contrasting two approaches

PDF) Extended Lagrange's four-square theorem

Pourchet's theorem in action: decomposing univariate nonnegative polynomials as sums of five squares

Spatial discontinuous Galerkin spectral element method for a family of chromatography models in CADET - ScienceDirect