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Stupid number trick III (Posted on 2006-01-11) Difficulty: 3 of 5
Pick any whole number greater than 1.

1. Write down all of its proper divisors (including 1 and the number itself)
2. Add the digits of these divisors.
3. Use this sum to repeat steps 1 and 2 until your number does not change.

Must the process terminate?
At what number(s) can the process terminate at?
What numbers <1000 take the most steps to terminate?

See The Solution Submitted by Jer    
Rating: 4.0000 (3 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re: Proof? | Comment 3 of 11 |
(In reply to Proof? by goFish)

I agree that this is the approach to a proof.  In fact, 48 is the largest value for which f(n) > n.  I'm not sure what the 7744 boundary means.

num3(2*3*5*7*11*13*17*19*23)
223092870 9594 279 47 12 19 11 3 4 7 8 15

                    ^- 9594>7744

What I really want is an interesting way to graphically display the tree that this forms.  I think it might look cool...perhaps fractal.


  Posted by Bob Smith on 2006-01-11 12:44:16
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