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4,4,4,4.... (Posted on 2007-07-31) Difficulty: 3 of 5
I chose a certain sequencing rule, and I told my friend no matter what number he named, it would eventually end up at repeating 4s.

At first he chose 5, which ended in 4, 4, 4... Then he tried 18, which met the same fate. Even numbers like -42 and Pi ended in 4, 4, 4...

Still trying to outdo me, he started to get really creative. He tried 63424563562324 ... same. He even tried a googolplex and Avogadro's number. But alas all the numbers he tried ended up in 4,4,4. Finally he conceded.

What's the sequencing rule I use? Should he have conceded? Can you find any starting terms which don't end in 4, 4, 4...?

See The Solution Submitted by jduval    
Rating: 4.3333 (3 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution Assumed there is a trick | Comment 4 of 8 |
Call the sequence P and x the starting number.  P(x,n) is the nth term of the sequence.

Sequencing rule: P(x,n) = 4

if you want a rule that does not work for all starting terms: 
P(x,n)= 4x/x is undefined if you start with zero.

  Posted by Jer on 2007-08-01 17:09:28
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