login
A174087
Number of circular permutations with no arithmetic progressions i, ..., i+r, ..., i+2r (mod n) of any equal spacings d.
3
4, 0, 12, 0, 96, 1296, 1520, 23540, 101472, 686724
OFFSET
4,1
COMMENTS
Circular permutations are permutations whose indices are from the ring of integers modulo n. Here we count both the sequence 1,2,3 (r=1) as a progression in 1,2,3,0,4,5, (note d=1) and in 1,0,2,4,3,5 (here, d=2).
LINKS
Peter Hegarty, Permutations avoiding arithmetic patterns, The Electronic Journal of Combinatorics, 11 (2004), #R39 (includes this sequence times n).
EXAMPLE
a(4) has the same value as A078628(4) since the only possible distance is 1.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Isaac Lambert, Apr 20 2010
STATUS
approved