

A187804


Number of circular permutations of length n whose n flattenings are all not derangements


0




OFFSET

3,3


COMMENTS

Circular permutations are permutations whose indices are from the ring of integers modulo n. For a circular permutation pi, a flattening at position k<n gives a straight permutation which preserves the relative order of pi. For example, the circular permutation (0,2,1) has the flattenings 021, 210, and 102. Note these three flattenings are all not derangements, so a(3) counts (0,2,1).


LINKS

Table of n, a(n) for n=3..10.


EXAMPLE

For n=5 the a(5)=3 solutions are (0,3,1,4,2), (0,4,3,2,1), and (0,2,4,1,3).


CROSSREFS

Sequence in context: A057398 A013579 A151814 * A281554 A320104 A102840
Adjacent sequences: A187801 A187802 A187803 * A187805 A187806 A187807


KEYWORD

nonn,more


AUTHOR

Isaac Lambert, Jan 06 2013


STATUS

approved



