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Old 2004-10-28, 11:18   #7
R.D. Silverman
 
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Nov 2003

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Quote:
Originally Posted by Andreas Schinde
I just did some trial division on 10^9999999+1 - the lowest odd 10 million digit number and found another small factor: 19 divides 10^9999999+1.

Other factors found so far (see also :this thread)

7 - found by heck
13 - can be read out of hecks table
11 - "manual" factoring using divisibility rule for p=11
Some intelligent, or with an understanding of 8th grade level first year
algebra might observe that if a is odd, then 10^(ab) + 1 is divisible by
10^b+1.

What is it that compels people to blindly throw a calculator or computer
at a problem *BEFORE* doing any thinking about the mathematics involved???
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