Enumeration of Partitions by Long Rises, Levels, and Descents
Toufik Mansour
Department of Mathematics
Haifa University
31905 Haifa
Israel
Augustine O. Munagi
The John Knopfmacher Centre for Applicable Analysis and Number Theory
School of Mathematics
University of the Witwatersrand
Johannesburg 2050
South Africa
Abstract:
When the partitions of [n] = {1, 2, ... , n} are identified with
the restricted growth functions on [n], under a known bijection,
certain enumeration problems for classical word statistics are
formulated for set partitions. In this paper we undertake the
enumeration of partitions of [n] with respect to the number of
occurrences of rises, levels, and descents, of
arbitrary integral length not exceeding n. This approach extends
previously known cases. We obtain ordinary generating functions for
the number of partitions with a specified number of occurrences of
the three statistics. We also derive explicit formulas for the
number of occurrences of each statistic among all partitions,
besides other combinatorial results.
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(Concerned with sequences
A000110
A052889
A105479
A105480
A105481
A105483
A105484
A105485 and
A105486.)
Received July 5 2008;
revised version received January 2 2009.
Published in Journal of Integer Sequences, January 3 2009.
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