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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
21, 94, 544, 3509, 26799, 223123
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).
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
Isaac Lambert, Apr 20 2010
STATUS
approved