[seqfan] Re: List the dividers, sum the digits
Frank Adams-Watters
franktaw at netscape.net
Sun Nov 8 00:57:04 CET 2015
The digit sum of 1,13 is 5, not 14. I get
10 -> 9 -> 13 -> 5 -> 6 -> 12 -> 19 -> 11 -> 3 -> 4 -> 7 -> 8 -> 15
Any loops are going to contain only small numbers; the digit sum reduces large numbers by a lot. Everything up to 13 is covered by the example above (adding 2 -> 3).
We have 14 -> 15; 16 -> 22 -> 9, 17 -> 9, 18 -> 30 -> 27 -> 22, and 20 -> 15, so everything 1 to 20 gets to 15.
I suspect 1 and 15 are the only loops.
Franklin T. Adams-Watters
-----Original Message-----
From: Eric Angelini <Eric.Angelini at kntv.be>
To: Sequence Discussion list <seqfan at list.seqfan.eu>
Sent: Sat, Nov 7, 2015 4:46 pm
Subject: [seqfan] List the dividers, sum the digits
Hello SeqFans,
1) list all dividers of A (1 and A included) ;
2) sum all
digits of the above list ;
3) iterate
Example for A=10:
10--> 1,10,2,5
dig.sum=9
9--> 1,9,3 dig.sum=13
13--> 1,13 dig.sum=14
14-->
1,14,2,7 dig.sum=15
15--> 1,15,3,5 dig.sum=15 (fixed point)
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