

A174084


Number of permutations of length n with no consecutive triples i,...i+r,...i+2r for all r, and for all equal spacings d.


3




OFFSET

4,1


COMMENTS

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



EXAMPLE

For n=4 there are 4!a(4)=3 with some progression. These are (0,1,2,3), (1,2,3,0), and (3,0,1,2). Here for all the progressions, r=1 and d=1, hence this term is the same as a(4) in A002628.


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



