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Squares sum up to a prime (Posted on 2017-01-13) Difficulty: 3 of 5
List all integers n such that the sum 2^2 + 3^2 + 4^2 + ... + n^2 equals a prime number. p&p solutions only.

See The Solution Submitted by Ady TZIDON    
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Hints/Tips re: solution | Comment 3 of 4 |
(In reply to solution by xdog)

(n-1)*(2n^2 +5n + 6)/6. 

should be presented as
(n-1)/6 * (2n^2 +5n + 6) 
to be coherent with  defining  (n-1)/6  as the 1st factor


  Posted by Ady TZIDON on 2017-01-13 22:24:02
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