prove that prime is uniquly expreesed as sum of two square number if and only if that prime is 4k+1

Remember, that any prime greater than 5 can be written as the sum of two or more primes. There are infinitely many primes of the form: 4k+1.

Here's the proof........good luck!!!! [ It's way above my pay grade......!!!! ]

http://www.artofproblemsolving.com/wiki/index.php/Fermat's_Two_Squares_Theorem