Poincaré polynomial for fully commutative elements in the symmetric group
Sadek AL Harbat, Corinne Blondel·2020-10-07·via math.CO updates on arXiv.org
Let $W^c(A_n)$ be the set of fully commutative elements of the Coxeter group $W(A_n)$. Let $$ a_n(q)= \sum_{w \in W^c(A_n)} q^{l(w)} . $$ We compute $a_n(q)$.