Waring's Problem -- from Wolfram MathWorld

Table 1 from Extended Lagrange's four-square theorem

Sums of four squares — AnhThu Nguyen

Lagrange's four-square theorem - Wikiwand

Number Theory Sums of Squares Part 7.

Pythagorean 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

Theorems Rectangle Rhombus Square (examples, solutions, worksheets, videos, games, activities)

Euler's four-square identity - Wikipedia

SOLUTION: Legendre's two, three and four square theorem (number theory) - Studypool