OFFSET
1,2
COMMENTS
These permutations satisfy the condition that their descent set corresponds with a composition which is weakly decreasing under the bijection between subsets of {1,2,...,n-1} to strict compositions of n via {d_1<d_2<...<d_k} maps to (d_1,d_2-d_1,...,d_k-d_k-1,n-d_k)
REFERENCES
R. P. Stanley, Enumerative Combinatorics, Wadsworth, Vol. 1, 1986, Vol. 2, 1999; see especially Chapter 1.
R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999 (Chapter 7)
EXAMPLE
For n=3, the 4 partition-type permutations are (1 2 3) (1 3 2) (2 3 1) (3 2 1).
CROSSREFS
KEYWORD
hard,nice,nonn
AUTHOR
Sara Billey, Sep 25 2008
STATUS
approved