OFFSET
0,3
COMMENTS
Equivalent definitions:
(1) Permutations that have the form (a_1, a_2, ..., a_k, b_1, b_2, ..., b_(n - k)), where the subsequences (a_1, a_2, ..., a_k) and (b_1, b_2, ..., b_(n - k)) avoid the permutation pattern 2143 and a_i < b_j for all i, j.
(2) Permutations that avoid the nine permutation patterns 24153, 25143, 31524, 31542, 32514, 32541, 42153, 52143, and 214365.
LINKS
Joel B. Lewis, Table of n, a(n) for n = 0..50
A. J. Klein, J. B. Lewis and A. H. Morales, Counting matrices over finite fields with support on skew Young diagrams and complements of Rothe diagrams.
R. J. Mathar, D-finite recurrence
FORMULA
Ordinary g.f. is (1 - x)*V(x)^2 - V(x) + 1/(1 - x), where V(x) is the (ordinary) g.f. for A005802.
CROSSREFS
KEYWORD
nonn
AUTHOR
Joel B. Lewis, May 29 2012
STATUS
approved