Restricted set of patterns, continued fractions, and Chebyshev polynomials
arXiv:math/0108043
Abstract
We study generating functions for the number of permutations in subject to set of restrictions. One of the restrictions belongs to , while the others to . It turns out that in a large variety of cases the answer can be expressed via continued fractions, and Chebyshev polynomials of the second kind.
9 pages