Math 222: Combinatorics

Professor: Jonah Blasiak

Fall 2021

Monday, Wednesday, Friday 11:00am - 11:50am, Academic Building 217

Course Description: Select combinatorial topics such as induction, generating functions, inclusion-exclusion, and graph theory. Emphasis on proof writing.
Prerequisites: Math 220.
Office Hours: Korman 275, Tuesday 3:30pm-5pm, Friday 12pm-1pm.
Problem Session: Korman 241, Tuesday 3pm-5pm.
Textbooks: We will use a combination of the following texts:
  • Discrete Mathematics: Elementary and Beyond, by L. Lovász, J. Pelikán, and K. Vesztergombi (Drexel Library online copy)
  • Introduction to Graph Theory, 2nd Edition, by Douglas B. West
  • Enumerative Combinatorics, vol.1, by R.P.Stanley
  • generatingfunctionology by Herbert Wilf
  • Grade Breakdown:
  • 10% Quiz
  • 20% Midterm
  • 30% Homework
  • 40% Final
  • Grading Policy:
  • A: 80-100%
  • B: 60-80%
  • C: 40-60%
  • D-F: 0-40%
  • Exam Policy: No books or electronic devices are allowed on the midterm or exam. No collaboration is permitted at the midterm or exam. THERE WILL BE NO MAKE-UPS FOR EXAMS.
    The midterm will be in-class on Wednesday, October 20; it will be 50 minutes long. Students with special exam-taking requirements or time conflicts should contact me by October 1.
    Quiz Policy: There will be one 25 minute quiz on Wednesday, October 13 (note this was changed from an earlier version of the syllabus). It can be thought of as practice for the midterm. No books or electronic devices are allowed on quizzes. No collaboration is permitted on quizzes. THERE WILL BE NO MAKE-UPS FOR QUIZZES.
    Homework Policy: You may consult each other and the textbook above. List all people and sources who aided you and whom you aided, and write up the solutions independently, in your own language. It is easy nowadays to find solutions to almost anything online. DO NOT consult such solutions until after turning your homework. Solutions to homeworks will be handed out in class and/or discussed in class. Late homeworks will not be accepted.
    Please visit this site frequently for new information. Updates to the syllabus and reading assignments, homeworks, and practice exams will be posted here as the course progresses.

    Syllabus

    Since we are using multiple textbooks, there will be some overlap with the reading assignments. The most important/relevant sources will be listed first.

    Week 1: Sep 20, Sep 22, Sep 24
    Set theory, functions, and the watermelon cutting problem: read the handout Joy of Sets, Section 1.2 and Theorem 1.3.1 of LPV (the textbook Discrete Mathematics: Elementary and Beyond).
    Read the handout Mathematical Hygiene. We will discuss some of these concepts throughout the course as needed.
    Homework 1 due Sep 29
    Correction: In Problem 1.9, the right hand side of the recurrence should have a factor m+1 in front, not m.

    Week 2: Sep 27, Sep 29, Oct 01
    Pascal's triangle, counting, bijective proofs, inclusion-exclusion: Sections 1.7-1.8, 3.5-3.6, 2.3 of LPV
    Wikipedia article on inclusion-exclusion
    Homework 2 due Oct 6.

    Week 3: Oct 04, Oct 06, Oct 08
    Inclusion-exclusion, Fibonacci numbers: Sections 6.9, 4.1-4.3 of LPV
    Homework 3. Update 10/14/21: Homework 3 is now due Monday Oct 18 since we did not cover domino tilings on Wednesday.

    Week 4: Oct 13, Oct 15
    Fibonacci numbers, generating functions: 1.1-1.3, 2.1-2.2 of generatingfunctionology
    There will be a 25 minute quiz at the end of class on Wednesday, October 13. About half the points will be proofs and half short answer. It will mainly cover the material on homeworks 1 and 2 and may include anything we covered in class up to but not including inclusion-exclusion.
    Homework 4 due Oct 27 (no homework due October 20 because of the midterm)

    Week 5: Oct 18, Oct 20, Oct 22
    Generating functions continued: 1.1-1.3, 2.1-2.2 of generatingfunctionology
    Midterm: Wednesday, October 20 in class.

    Week 6: Oct 25, Oct 27, Oct 29
    Catalan numbers, generating functions: Chapter 2 of generatingfunctionology
    Homework 5 due Nov 10

    Week 7: Nov 1, Nov 3, Nov 5
    Introduction to graph theory: vertex degrees, trees, paths, cycles: Ch. 1-2 of West or Sections 7.1-7.2, 8.1-8.2, 13.2 of LPV

    Week 8: Nov 8, Nov 10, Nov 12
    Trees, Kruskal's algorithm: Ch. 2 of West
    Homework 6 due Nov 17

    Week 9: Nov 15, Nov 17, Nov 19
    Euler's formula, Platonic solids, Graph coloring: Ch. 6.1 and 5.1 of West

    Week 10: Nov 22
    Coloring planar graphs: Ch. 6.3 of West

    Week 11: Nov 29, Dec 01, Dec 03
    Hall's matching theorem: Ch. 3 of West


    Homework Help: Math Resource Center (Korman 247)
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    Academic Dishonesty

    Course Drop Policy

    Code of Conduct

    Disability Resources:
    Students requesting accommodations due to a disability at Drexel University need to request a current Accommodations Verification Letter (AVL) in the ClockWork database before accommodations can be made. These requests are received by Disability Resources (DR), who then issues the AVL to the appropriate contacts. For additional information, visit the DR website at drexel.edu/oed/disabilityResources/overview/, or contact DR for more information by phone at 215.895.1401, or by email at disability@drexel.edu.

    Outcomes: Students must understand basic mathematical language including sets and functions, apply mathematical induction, count or enumerate objects using various combinatorial formulas, operate with discrete structures including graphs and permutations, and describe simple algorithms. Students will be comfortable writing short mathematical proofs including proofs by induction, bijective proofs, and proofs in number theory.