Thursday, May 29, 2014

138: Largest Integer

What is the largest even integer that cannot be written as the sum of two odd composite numbers?

For example, 42 = 21 + 21, so it is not a candidate. 22 is a candidate because no pair of 9, 15, or 21 can equal 22.

As with many of Mr. Tanton's puzzles, there's a way to know that you are absolutely correct. Can you find the number and the explanation?

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