Sum of two squares theorem - Wikipedia

PDF) Two refinements of Lagrange's four-square theorem

PDF) Algebraic Consequences of Jacobi's Two- and Four-Square Theorems

SOLVED: 8.35 (Lagrange's Four-Square Theorem) If n is a natural number, it can be expressed as the sum of four squares. A lattice in 4-space is a set of the form (x,y,z,w)

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

Lagrange's Four Square Theorem

number theory - The Four Square Theorem and Integral Apollonian Circle Packings, is there any connection? - Mathematics Stack Exchange

Sum of squares, Part-2, Sum of four squares

Sum of Squares Function -- from Wolfram MathWorld

Waring's Problem -- from Wolfram MathWorld

MathType - Lagrange's four-square theorem states that every natural number can be represented as the sum of four integer squares. Proved by Joseph Louis #Lagrange in 1770, it can be regarded as