關於此課程：Enumerative combinatorics deals with finite sets and their cardinalities. In other words, a typical problem of enumerative combinatorics is to find the number of ways a certain pattern can be formed. In the first part of our course we will be dealing with elementary combinatorial objects and notions: permutations, combinations, compositions, Fibonacci and Catalan numbers etc. In the second part of the course we introduce the notion of generating functions and use it to study recurrence relations and partition numbers. The course is mostly self-contained. However, some acquaintance with basic linear algebra and analysis (including Taylor series expansion) may be very helpful.
此課程適用人群：This course is primarily aimed at the Master of Science students of Mathematics department. Students are expected to have knowledge of one-semester courses of advanced calculus and linear algebra.
製作方： National Research University Higher School of Economics
教學方： Evgeny Smirnov, Associate Professor
Faculty of Mathematics
| 級別 | 中級 |
| 承諾學習時間 | 8 weeks, 10-12 hours per week |
| 語言 | English |
| 如何通過 | 通過所有計分作業以完成課程。 |
| 用戶評分 |
授課大綱
第 1 週
Introduction
1 個視頻, 4 個閱讀材料
- Reading: Course Overview
- Reading: Grading and Logistics
- Reading: Suggested Readings
- Reading: About the Instructor
Permutations and binomial coefficients
In this introductory lecture we discuss fundamental combinatorial constructions: we will see how to compute the number of words of fixed length in a given alphabet, the number of permutations of a finite set and the number of subsets with a given number of elements in a finite set. The latter numbers are called binomial coefficients; we will see how they appear in various combinatorial problems in this and forthcoming lectures. As an application of combinatorial methods, we also give a combinatorial proof of Fermat's little theorem.
7 個視頻
- 視頻: Permutations
- 視頻: k-permutations
- 視頻: Merry-go-rounds and Fermat’s little theorem 1
- 視頻: Merry-go-rounds and Fermat’s little theorem 2
- 視頻: Binomial coefficients
- 視頻: The Pascal triangle
已評分: Quiz 2
第 2 週
Binomial coefficients, continued. Inclusion and exclusion formula.
In the first part of this lecture we will see more applications of binomial coefficients, in particular, their appearance in counting multisets. The second part is devoted to the principle of inclusion and exclusion: a technique which allows us to find the number of elements in the union of several sets, given the cardinalities of all of their intersections. We discuss its applications to various combinatorial problem, including the computation of the number of permutations without fixed points (the derangement problem).
7 個視頻
- 視頻: Balls in boxes and multisets 1
- 視頻: Balls in boxes and multisets 2
- 視頻: Integer compositions
- 視頻: Principle of inclusion and exclusion: two examples
- 視頻: Principle of inclusion and exclusion: general statement
- 視頻: The derangement problem
已評分: Quiz 3
第 3 週
Linear recurrences. The Fibonacci sequence
We start with a well-known "rabbit problem", which dates back to Fibonacci. Using the Fibonacci sequence as our main example, we discuss a general method of solving linear recurrences with constant coefficients.
11 個視頻, 1 個閱讀材料
- 視頻: Fibonacci numbers and the Pascal triangle
- 視頻: Domino tilings
- 視頻: Vending machine problem
- 視頻: Linear recurrence relations: definition
- 視頻: The characteristic equation
- 視頻: Linear recurrence relations of order 2
- 視頻: The Binet formula
- 視頻: Sidebar: the golden ratio
- 視頻: Linear recurrence relations of arbitrary order
- 視頻: The case of roots with multiplicities
- Reading: Spoilers! Solutions for quizzes 2, 3, and 4.
已評分: Quiz 4
第 4 週
A nonlinear recurrence: many faces of Catalan numbers
In this lecture we introduce Catalan numbers and discuss several ways to define them: via triangulations of a polygon, Dyck paths and binary trees. We also prove an explicit formula for Catalan numbers.
7 個視頻, 1 個閱讀材料
- 視頻: Recurrence relation for triangulations
- 視頻: The cashier problem
- 視頻: Dyck paths
- 視頻: Recurrence relations for Dyck paths
- 視頻: Reflection trick and a formula for Catalan numbers
- 視頻: Binary trees
- Reading: Solutions
已評分: Graded assignment 1 (midterm exam)
第 5 週
Generating functions: a unified approach to combinatorial problems. Solving linear recurrences
We introduce the central notion of our course, the notion of a generating function. We start with studying properties of formal power series and then apply the machinery of generating functions to solving linear recurrence relations.
9 個視頻, 1 個閱讀材料
- 視頻: Formal power series
- 視頻: When are formal power series invertible?
- 視頻: Derivation of formal power series
- 視頻: Binomial theorem for negative integer exponents
- 視頻: Solving the Fibonacci recurrence relation
- 視頻: Solving the Fibonacci recurrence 2: Binet formula
- 視頻: Generating functions of linear recurrence relations are rational
- 視頻: Solving linear recurrence relations: general case
- Reading: Math expressions
已評分: Quiz 6
第 6 週
Generating functions, continued. Generating function of the Catalan sequence
In this lecture we discuss further properties of formal power series. In particular, we prove an analogue of the binomial theorem for an arbitrary rational exponent. We apply this technique to computing the generating function of the sequence of Catalan numbers.
6 個視頻
- 視頻: Derivation and integration of formal power series
- 視頻: Chain rule. Inverse function theorem
- 視頻: Logarithm. Logarithmic derivative
- 視頻: Binomial theorem for arbitrary exponents
- 視頻: Generating function for Catalan numbers
已評分: Quiz 7
第 7 週
Partitions. Euler’s generating function for partitions and pentagonal formula
In this lecture we introduce partitions, i.e. the number of ways to present a given integer as a sum of ordered integer summands. There is no closed formula for the number of partitions; however, it is possible to compute their generating function. We study the properties of this generating function, including the famous Pentagonal theorem, due to Leonhard Euler.
9 個視頻, 1 個閱讀材料
- 視頻: Young diagrams
- 視頻: Generating function for partitions
- 視頻: Partitions with odd and distinct summands
- 視頻: Sylvester’s bijection
- 視頻: Euler’s pentagonal theorem
- 視頻: Proof of Euler’s pentagonal theorem 1
- 視頻: Proof of Euler’s pentagonal theorem 2
- 視頻: Computing the number of partitions via the pentagonal theorem
- Reading: Spoilers! Solutions for quizzes 6, 7, and 8.
已評分: Quiz 8
第 8 週
Gaussian binomial coefficients. “Quantum” versions of combinatorial identities
Our final lecture is devoted to the so-called "q-analogues" of various combinatorial notions and identities. As a general principle, we replace identities with numbers by identities with polynomials in a certain variable, usually denoted by q, that return the original statement as q tends to 1. This approach turns out to be extremely useful in various branches of mathematics, from number theory to representation theory.
8 個視頻, 1 個閱讀材料
- 視頻: q-binomial coefficients: definition and first properties
- 視頻: Recurrence relation for q-binomial coefficients 1
- 視頻: Recurrence relation for q-binomial coefficients 2
- 視頻: Explicit formula for q-binomial coefficients
- 視頻: Euler’s partition function
- 視頻: Sidebar: q-binomial coefficients in linear algebra
- 視頻: q-binomial theorem
- Reading: Solutions
已評分: Graded assignment 2 (final exam)
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製作方
National Research University Higher School of Economics
National Research University - Higher School of Economics (HSE) is one of the top research universities in Russia. Established in 1992 to promote new research and teaching in economics and related disciplines, it now offers programs at all levels of university education across an extraordinary range of fields of study including business, sociology, cultural studies, philosophy, political science, international relations, law, Asian studies, media and communications, IT, mathematics, engineering, and more.
Learn more on www.hse.ru
評分和審閱
Funny
Very good presentation
Excellent selection of material and presentation; TAs were of great help as well. The techniques taught in this course will be a nice addition to my algorithms analysis toolbox.
by far the best math course I had (and I've taken many) on coursera
DS
Nice work!