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

Table 1 from Extended Lagrange's four-square theorem

PDF) Lagrange's Four-Square Theorem

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

Lagrange's four-square theorem

Table 3 from Extended Lagrange's four-square theorem

PDF) A Simple Proof of Jacobi's Four-Square Theorem

SOLVED: Theorem 8.35 (Lagrange's Four-Square Theorem) then n can be expressed as the sum If n is a number; of four squares: natural lattice A in 4-space is a set of the

Square Number Definition & Meaning

FERMAT'S FOUR SQUARES THEOREM Several years ago, after

GitHub - HechenHu/Four-Square_Representation: Using Rabin and Shallit's Algorithm to compute the four-square representation of a natural number as stated in Lagrange's Four-square Theorem.