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Some 2 Powers Sum to Factorial (Posted on 2023-02-27) Difficulty: 3 of 5
Determine all possible triplets (p, q, n) of nonnegative integers that satisfy this equation:
                 2p + 2q = n! 
Provide valid argument for your answer.

*** Adapted from a problem which appeared at the Harvard/MIT math Olympiad.

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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Some Thoughts Another approach Comment 5 of 5 |
When converted to binary, 2^p + 2^q will yield a binary number having only two digits equal to 1 and all other digits equal to 0.  If you factored every positive integer, converted the result to binary, and then added the sum of the digits, any sum equal to 2 would satisfy the equation.

Using Excel:

3! = 110
4! = 11000

  Posted by hoodat on 2023-02-28 16:09:47
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