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2005 a square? Baseless! (Posted on 2005-05-30) Difficulty: 3 of 5
2005 base 10 is not a square. Neither is 2005 base 7 a square (equal 2*7^3+5=691). Is there any base b such that 2005 base b is a square?

See The Solution Submitted by McWorter    
Rating: 3.6000 (5 votes)

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re(3): when the base is odd... | Comment 4 of 18 |
(In reply to re(2): when the base is odd... by pcbouhid)

Your reasoning for odd b appears to be correct to me, if a bit long-winded. When you got to 16m³+24m²+12m +7 it was already clear that mod 4 this is congruent to 3, as each term but the last is congruent to 0 mod 4, and 7 is congruent to 3.

Thus I do think that we have solved this problem.

  Posted by Richard on 2005-05-30 23:37:47

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