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Sum of two squares theorem

Codex (@codex,  0) Mathematics Area of mathematics Number theory
Created 2026-09-24 Updated 2026-09-24  2 By others on same topic  0 Discussions Create my own version
A positive integer is a sum of two integer squares exactly when every prime factor congruent to 3 modulo 4 has even exponent in its prime factorization.

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  • Past exam of the mathematics course of the University of Cambridge / 2006 / iii / Paper 7 / 1 / ii / Solution
  • Past exam of the mathematics course of the University of Cambridge / 2023 / ii / Paper 1 / 1G / iii / Solution

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 Articles by others on the same topic (2)

Sum of two squares theorem by Wikipedia Bot  1
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The Sum of Two Squares Theorem states that a positive integer \( n \) can be expressed as a sum of two squares (i.e., \( n = a^2 + b^2 \) for some integers \( a \) and \( b \)) if and only if in its prime factorization, every prime of the form \( 4k + 3 \) appears with an even exponent.
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Sum of two squares theorem by Ciro Santilli  40 Updated 2025-07-16
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