274 research outputs found
Part-products of -restricted integer compositions
If is a cofinite set of positive integers, an "-restricted composition
of " is a sequence of elements of , denoted
, whose sum is . For uniform random
-restricted compositions, the random variable is asymptotically lognormal. The proof is
based upon a combinatorial technique for decomposing a composition into a
sequence of smaller compositions.Comment: 18 page
S-Restricted Compositions Revisited
An S-restricted composition of a positive integer n is an ordered partition
of n where each summand is drawn from a given subset S of positive integers.
There are various problems regarding such compositions which have received
attention in recent years. This paper is an attempt at finding a closed- form
formula for the number of S-restricted compositions of n. To do so, we reduce
the problem to finding solutions to corresponding so-called interpreters which
are linear homogeneous recurrence relations with constant coefficients. Then,
we reduce interpreters to Diophantine equations. Such equations are not in
general solvable. Thus, we restrict our attention to those S-restricted
composition problems whose interpreters have a small number of coefficients,
thereby leading to solvable Diophantine equations. The formalism developed is
then used to study the integer sequences related to some well-known cases of
the S-restricted composition problem
A Note on Extended Binomial Coefficients
We study the distribution of the extended binomial coefficients by deriving a
complete asymptotic expansion with uniform error terms. We obtain the expansion
from a local central limit theorem and we state all coefficients explicitly as
sums of Hermite polynomials and Bernoulli numbers
A Discontinuity in the Distribution of Fixed Point Sums
The quantity , defined as the number of permutations of the set
whose fixed points sum to , shows a sharp discontinuity
in the neighborhood of . We explain this discontinuity and study the
possible existence of other discontinuities in for permutations. We
generalize our results to other families of structures that exhibit the same
kind of discontinuities, by studying when ``fixed points'' is replaced
by ``components of size 1'' in a suitable graph of the structure. Among the
objects considered are permutations, all functions and set partitions.Comment: 1 figur
Counting Permutations by Their Rigid Patterns
AbstractIn how many permutations does the patternτ occur exactly m times? In most cases, the answer is unknown. When we search for rigid patterns, on the other hand, we obtain exact formulas for the solution, in all cases considered
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