Math 580

Fall 2008

Professor: Eric Egge

Email: eegge at math dot (five letter school name) dot edu

Phone: 8-5988

Office Hours: Mondays from 1 pm to 2 pm, Wednesdays from 9:45 am to 10:45 am, and Thursdays from 2:30 pm to 3:30 pm, in DRL 3C3. I am also available by appointment.

Course Meetings: Mondays and Fridays from 10:30 am to noon in DRL 4N30.

Grades: Homework is worth 10%, the First Exam is worth 25%, the Second Exam is worth 25%, and the Final Exam is worth 40%.

Homework: There will be recommended homework assignments (not to be turned in) and, approximately every other week, some required homework assignments (to be turned in and graded). I encourage you to discuss the problems with each other or me, but I require the write-ups of the homework solutions to be your own. Your write-ups should be as neat as possible, with complete, appropriately organized, clearly explained solutions.

First and Second Exams: These exams will be given in class on Friday, October 10, and Monday, November 10, respectively.

Final Exam: The final exam will be from noon to 2 pm on Friday, December 12, location to be announced later. This exam will be cumulative.

This course is intended to be an introduction to enumerative combinatorics suitable for advanced undergraduates or graduate students in mathematics. The primary text for the course will be Enumerative Combinatorics, volume 1, by Richard Stanley, but in order to gain an appreciation for some recent work in the area, we will also cover selected material from Combinatorics of Permutations, by Miklos Bona, Proofs and Confirmations, by David M. Bressoud, The Symmetric Group, by Bruce Sagan, and Enumerative Combinatorics, volume 2, by Richard Stanley. A good supplemental reference for the course will be generatingfunctionology, by Herb Wilf, which available free at his website. Specific topics we will cover include basic objects in enumeration, such as generating functions, permutation statistics, Eulerian polynomials, multiset permutations, q-Binomial Coefficients, the Twelvefold Way, Stirling, Catalan, and Bell Numbers; the theory of rational generating functions, including the transfer matrix method; recent results in pattern-avoiding permutations, including the Marcus-Tardos theorem; and sieve methods, including inclusion-exclusion. As time permits, we will also study basic combinatorics of symmetric functions, including the hook length formula; and alternating sign matrices and plane partitions.

Homework Assignments

Required Homework for Friday, December 5

Worksheet Problems

Recommended Homework for Monday, December 1

This homework set is from Bressoud's book Proofs and Confirmations, which is on reserve in the Math Library, in DRL 3N1.

Read Sections 3.2 and 3.3.

Required Homework for Monday, November 24

Worksheet Problems

Recommended Homework for Friday, November 21

This homework set is from Bressoud's book Proofs and Confirmations, which is on reserve in the Math Library, in DRL 3N1.

Read Sections 1.2 and 2.2.
Section 1.2: 5, 6
Section 2.2: 11
Section 3.1: 19
Prove that p(n) = (1/n) \sum_{j=1}^n \sigma_1(j) p(n-j).

Recommended Homework for Monday, November 17

This homework set is from Bressoud's book Proofs and Confirmations, which is on reserve in the Math Library, in DRL 3N1.

Read Sections 1.1 and 3.1.
Section 1.1: 7, 10
Section 3.1: 1, 12

Recommended Homework for Friday, November 7

Read Section 2.2.
Chapter 2: 1, 10

Recommended Homework for Monday, November 2

Read Section 2.1.
Read the Stanley-Wilf handout.
Find a continued fraction expansion for the sum of x^{|\pi|} q^{inv(\pi)} over all permutations which avoid 312.
Find the generating function for |S_n(312,1324)|.
Give a combinatorial proof that D_n = (n-1)(D_{n-1} + D_{n-2}).
Chapter 2: 7

Required Homework for Monday, October 27.

Worksheet Problems

Recommended Homework for Friday, October 24

Show that if U_n(cos z) = sin((n+1)z)/sin(z) then U_n(x) = 2x U_{n-1}(x) - U_{n-2}(x).
Find |S_n(312,54321)| for n < 11.
Find and prove a formula for |S_n(312,2143)|.
Find and prove a formula for the number of permutations in S_n(123) with exactly k left to right minima.

Recommended Homework for Monday, October 20

Midterm evaluation form.
Find and prove a formula for |S_n(123,132)|.
Find and prove a formula for the number of permutations of length 2n+1 which avoid 123 and are invariant under the reverse-complement map rc.
Show that |S_n(123,132)| = |S_n(123,213)| for all n.

Recommended Homework for Monday, October 5

Read Section 4.7, up to ``Factorization in Free Monoids''

Required Homework for Friday, October 3

Worksheet Problems

Recommended Homework for Monday, September 29

Read Sections 4.1 and 4.2.
Chapter Four: 19ab
Show that the number of ways to place the numbers 1,2,...,2n in a 2xn array of 1x1 boxes so that the entries increase from left to right and from top to bottom is C_n.
Define T_0 = T_1 = T_2 = 1 and T_n = T_{n-1} + T_{n-2} + T_{n-3} for all n larger than 2. Find the ordinary generating function for T_0, T_1, ... and the limit as n goes to infinity of the nth root of T_n.

Recommended Homework for Friday, September 26

Chapter One: 17, 23a, 29, 30ab

Recommended Homework for Monday, September 22

Read Section 1.4.
Chapter One: 11, 21, 22

Required Homework for Friday, September 19

Chapter One: 2a or 2c, 4, 14i, 32, 33

Recommended Homework for Monday, September 15

Chapter One: 1ij, 2d, 7, 43a

Recommended Homework for Friday, September 12

Read Section 1.3.
Chapter One: 1cdh, 3, 14bc

Recommended Homework for Monday, September 8

Read Sections 1.1 and 1.2.
Chapter One: 1afg, 2ab, 12, 14ae

Last Updated: November 20, 2008