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A false claim (Posted on 2013-02-05) Difficulty: 3 of 5
A German mathematician Christian Goldbach (1690-1764) stated that every odd composite number can be written as a sum of a prime and twice a square.

Some examples:
9 = 7 + 2*12
21 = 3 + 2*32
25 = 7 + 2*32
33 = 31 +2*12

Now we know that his conjecture is false.

What is the smallest odd composite number not complying with C.G.'s conjecture?

No Solution Yet Submitted by Ady TZIDON    
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Interesting Comment 2 of 2 |
Unfortunately I don't think there are any methods not using brute force to solve this.  But searching for the numbers found by Charlie gives

  Posted by Jer on 2013-02-06 12:33:29
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