Enumeration of Unigraphical Partitions
Michael D. Hirschhorn
School of Mathematics
UNSW
Sydney 2052
Australia
James A. Sellers
Department of Mathematics
The Pennsylvania State University
University Park, PA 16802
USA
Abstract:
In the early 1960s, S. L. Hakimi proved necessary and sufficient
conditions for a given sequence of positive integers
d1, d2, ...,
dn
to be the degree sequence of a unique graph (that is, one and only
one graph realization exists for such a degree sequence). Our goal in
this note is to utilize Hakimi's characterization to prove a closed
formula for the function duni(2 m),
the number of "unigraphical partitions" with degree sum 2m.
Full version: pdf,
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(Concerned with sequences
A000005
A000041
A001399 and
A083039
.)
Received September 6 2008;
revised version received October 8 2008.
Published in Journal of Integer Sequences, October 18 2008.
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