Euler's four-square identity

Seatings and Sums of Squares

Solved {(x,y,z,w).M: x,y,z, w € Z} Theorem 8.35 (Lagrange's

What's so interesting about squared numbers? Lagrange's Four Square Theorem

PDF) Extended Lagrange's four-square theorem

PDF] New parametrization of $A^2+B^2+C^2=3D^2$ and Lagrange's four-square theorem

Pythagorean Theorem

CodeChef - Lagrange's four-square theorem, also known as Bachet's conjecture, states that every natural number can be represented as the sum of four integer squares. This theorem was proven by Joseph Louis

Why was this visual proof missed for 400 years? (Fermat's two square theorem)

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

Proving the Pythagorean Theorem. Some algebraic and geometric proofs of…, by Michele Diodati, Not Zero