Divisor chains
Richard Guy
rkg at cpsc.ucalgary.ca
Mon May 3 22:20:45 CEST 2004
The following might be an acceptable sequence
for Neil Sloane's OEIS, but someone needs to
do some work
1 2 3 4 5 6 7 8 9 10 11 12 13 14 ...
1 1 1 1 1 1 1 5 4 1 2 5 5 4 ...
It arises from a problem I got recently from
Paul Vaderlind.
If the sequence of numbers from 1 to 37,
is arranged so that each term is a divisor
of the sum of preceding ones, starting
37, 1, ...
what is the next term?
The answer is either 2 or 19. P'r'aps
I won't spoil your fun by pointing out
which. But I will spoil it by asking:
How do you know that there is such a
`divisor chain' ?
The sequence is (my present state of knowledge
of) the number of divisor chains of length n.
Here are the ones I found
1 2 1 3 1 2 4 2 3 1
5 1 2 4 3 6 2 4 3 5 1 7 1 2 5 3 6 4
8 2 5 3 6 4 7 1
8 4 2 7 3 1 5 6
8 4 2 7 3 6 5 1
8 4 3 5 1 7 2 6
8 4 6 3 7 2 5 1
9 1 2 4 8 6 5 7 3
9 1 2 6 3 7 4 8 5
9 3 4 8 6 5 7 2 1
9 3 6 2 1 7 4 8 5
10 2 4 8 3 9 6 7 1 5
11 1 2 7 3 8 4 9 5 10 6
11 1 4 8 6 10 5 9 2 7 3
12 2 1 5 10 3 11 4 8 7 9 6
12 2 7 3 8 4 9 5 10 6 11 1
12 3 5 10 2 8 4 11 1 7 9 6
12 4 8 3 9 6 2 11 5 10 7 1
12 4 8 6 10 5 9 2 7 3 11 1
13 1 2 8 3 9 4 10 5 11 6 12 7
13 1 2 8 6 10 4 11 5 12 9 3 7
13 1 2 8 6 10 4 11 5 3 9 12 7
13 1 2 8 12 4 10 5 11 3 9 3 7
13 1 2 8 12 4 10 5 11 6 9 3 7
14 2 8 6 10 4 11 5 3 9 12 7 13 1
14 2 8 6 10 4 11 5 12 9 3 7 13 1
14 2 8 12 4 10 5 11 6 9 3 7 13 1
14 2 8 12 9 3 4 13 1 11 7 6 10 5
Enough sins of omission, to say nothing of
commission, for today. Please check and extend.
Any ideas for proving anything? R.
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