OFFSET
0,4
COMMENTS
Apparently this sequence originated in a problem composed by Matthijs Coster in 2002.
Let M = floor(n/2), then the following permutations always work: for n even: M+1, 1, M+2, 2, ..., n-1, M-1, n, M; for n odd: M+1, 1, M+2, 2, ..., M-1, n-1, M, n. - Daniel Asimov, May 04 2004
LINKS
Matthijs Coster, Sequences
Matthijs Coster, Problem 2001/3-A of the Universitaire Wiskunde Competitie, Nieuw Arch. Wisk. 5/3 (2002), 92-94.
EXAMPLE
Examples of divisor chains of lengths 1 through 9:
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 3 5 1 7 2 6 9
The five divisor chains of length 6 are:
4 1 5 2 6 3
4 2 6 3 5 1
5 1 2 4 6 3
5 1 6 4 2 3
6 2 4 3 5 1. - Eugene McDonnell, May 21 2004
CROSSREFS
KEYWORD
nonn
AUTHOR
Floor van Lamoen, Mar 06 2002
EXTENSIONS
a(31)-a(35) from Jud McCranie, May 06 2004
a(0)=1 prepended by Alois P. Heinz, Aug 26 2017
a(36)-a(41) from Zhao Hui Du, May 12 2024
STATUS
approved