Some Statistics on the Hypercubes of Catalan Permutations
Filippo Disanto
Department of Biology
Stanford University
Stanford, CA 94305
USA
Abstract:
For a permutation σ of length 3, we define the oriented graph
Qn(σ).
The graph Qn(σ)
is obtained by imposing edge constraints
on the classical oriented hypercube Qn,
such that each path going
from 0n to 1n in
Qn(σ)
bijectively encodes a permutation
of size n avoiding the pattern σ. The orientation of the edges
in
Qn(σ)
naturally induces an order relation ≼σ
among its nodes. First, we characterize ≼σ.
Next, we
study several enumerative statistics on
Qn(σ), including the
number of intervals, the number of intervals of fixed length k, and
the number of paths (or permutations) intersecting a given node.
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(Concerned with sequences
A000079
A000108
A000245
A000295
A001793
A009766
A038207
A047520
A065109.)
Received April 16 2014; revised version received November 11 2014; December 17 2014.
Published in Journal of Integer Sequences, January 24 2015.
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