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Enumerative combinatorics, graph theory, order theory, posets, matroids, designs and other discrete structures. It also includes algebraic, analytic and probabilistic combinatorics.

10 votes
Accepted

Number of binary strings with 'at least two consecutives' constraints

We start considering words with no consecutive equal characters at all. These words are called Smirnov words or Carlitz words. (See example III.24 Smirnov words from Analytic Combinatorics by Philipp …
Markus Scheuer's user avatar
2 votes

Important formulas in combinatorics

The asymptotic formula of the average number of comparisons used by the Quick Sort algorithm. \begin{align*} Q_n=2n(\ln n + \gamma -2)+2\ln n+2\gamma+1+O\left(\frac{1}{n}\right)\tag{1} \end{align*} …
7 votes

Asymptotics of coefficients of implicitely defined generating function

There are some papers by V. Kruchinin addressing the composition of generating functions Composita and its properties Composition of ordinary generating functions Derivation of Bell Polynomials of t …
Markus Scheuer's user avatar
7 votes
Accepted

Is there a simple proof of the following Identity for $\sum_{k=m-1}^l(-1)^{k+m}\frac{k+2}{k+...

We obtain for $l,m\in\mathbb{N}$ with $0\leq m-1 \leq l$: \begin{align*} \color{blue}{\sum_{k=m-1}^{l}}&\color{blue}{(-1)^{k+m}\frac{k+2}{k+1}\binom{l}{k}\binom{k+1}{m}}\\ &=\frac{1}{m}\sum_{k=m- …
Markus Scheuer's user avatar
1 vote

Proving a particular "Abel type" identiy

Here is a starter. We can simplify the RHS somewhat. We obtain \begin{align*} \frac{1}{2}& \sum_{{n_1+n_2=n-1}\atop{n_1,n_2\geq 0}}\left[ (n_1+1)^{n_1-1} (n_2-2\ell+1)^{n_2} \binom{n_2}{\ell-1}\ …
Markus Scheuer's user avatar
3 votes
Accepted

Is there a simple proof of the following binomial Identity (part 2)?

Following the hint @darijgrinberg stated in the comment section with respect to the beauty inside the square brackets we focus on the sum and we obtain \begin{align*} \color{blue}{\sum_{k=m+ …
Markus Scheuer's user avatar
3 votes

Combinatorial aspects of continued fractions

Hint: No book recommendation, but in case you are not aware of it you might appreciate the nice survey Combinatorial aspects of continued fractions and applications by Xavier G. Viennot in honor of …
Markus Scheuer's user avatar