# Legendre's three-square theorem

> theorem that every nonnegative integer is the sum of three perfect squares unless it is a product of a power of four and a number that is 7 modulo 8

**Wikidata**: [Q15940470](https://www.wikidata.org/wiki/Q15940470)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Legendre's_three-square_theorem)  
**Source**: https://4ort.xyz/entity/legendre-s-three-square-theorem