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How about 138? (Posted on 2018-05-10) Difficulty: 4 of 5
Let us define a sequence S(N): a1= N,
an= sum of all factors of an-1, excluding an-1 itself. Most sequences either converge or begin to repeat.

S(12) → 12,16,15,9,4,3,1,1,1...
S(6) → 6,6,6,6,...
S(220) → 220,284,220,284,220,284,...
Try to evaluate S(50), S(80), S(99).

How about S(138)?
WILL IT CONVERGE TO 1,1,1,...?
Please comment!

No Solution Yet Submitted by Ady TZIDON    
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Comments: ( Back to comment list | You must be logged in to post comments.)
Link to a spoiler | Comment 2 of 4 |
https://oeis.org/A008888
  Posted by Jer on 2018-05-10 14:32:58
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