Cached Sept. 22, 2007, from
http://www.math.harvard.edu/~mantovan/ADMIN/syllabus28.html

The syllabus below is undated, but is prior to 2007.

Quantitative Reasoning 28

The Magic of Numbers

Catalog description

This course will explore the beauty and mystery of mathematics through a study of the patterns and properties of the natural numbers 1,2,3... . We'll discuss various special classes of numbers, like Fibonacci numbers, factorials and binomials and the many ways they arise in mathematics and nature. We'll also investigate the mysterious behavior of the prime numbers and their distribution, and alternative counting systems such as modular arithmetic.

Prerequisites

We will assume no mathematical background beyond high school algebra. Emphasis will be placed on discovery through conjecture and experimentation.

Faculty

NameOfficeE-mail address
Benedict GrossScience Center 326 gross@math.harvard.edu
Joseph HarrisScience Center 339 harris@math.harvard.edu

Teaching Fellows

NameOfficeE-mail address
Laura De MarcoScience Center 321d demarco@math.harvard.edu
Mark LucianovicScience Center 431e markl@math.harvard.edu
Elena MantovanScience Center 425e mantovan@math.harvard.edu
Nick RogersScience Center 333g nfrogers@math.harvard.edu

Course Website

www.courses.fas.harvard.edu/~qr28

Textbooks

Ivan Niven, Mathematics of Choice: Or, How to Count Without Counting
Constance Reid, From Zero to Infinity

See the website www.fas.harvard.edu/~ucbooks to order these books online.

Sourcebook Materials

Philip Davis and Reuben Hersh, The Prime Number Theorem.
Benedict Gross and Joe Harris, The Magic of Numbers.
Benedict Gross and Joe Harris, Catalan Numbers.
Paul Hoffman, Archimedes' Revenge.
Malcolm Lines, Think of a Number.
Edgar Allan Poe, The Gold-Bug
Tom Weston, Infinity.

The sourcebook is available in the Science Center basement.

Homework

There will be short homework assignments after each lecture. The homework will be designed to review concepts from the previous lecture, to reinforce topics in the reading and to introduce some of the ideas of the next lecture. All of the homework questions will be posted on the course's website; they will not be handed out in class. Homework is due the lecture after it is assigned. Absolutely no late homework will be accepted.

Exams

There will be two midterm examinations during the semester and a final exam during the finals period. The midterms will be given during class on Friday, October 12th and Friday, November 16th. Notify one of the teaching fellows as soon as possible if you have a conflict with one of the exam times. The final exam will be scheduled by the registrar's office.

Grading Policy

The final grade will be based on the homework, the two midterms, and the final. The homework and each midterm will count for about 20% of the final grade, and the final exam will count for about 40% of the final grade. Minor adjustments may be made to take into account improvement during the semester.

Sections

Section times will be announced in the second week of the course, based upon the students' schedules. These will meet for one hour per week. In section we will review some topics from lecture and explore related issues. Section attendance is required. We will ask you on Friday for the openings in your schedules and over the weekend we will post your section times on the course website.

Schedule

Below is the tentative lecture schedule for the course. It may change somewhat depending on the length of time required for certain topics and student interest.

Wednesday, September 12: The Remarkable Fibonacci numbers

Arithmetic and geometric progressions; patterns among Fibonacci numbers; examples in nature.

Lines, Chapter 2

Friday, September 14: Infinity

Examples of infinite sets; The Hotel Infinity; countable and uncountable infinities; arithmetic with infinity.

Reid, Chapter aleph0
Weston, Infinity

Monday, September 17: How to count without counting I

Counting problems; the principle of multiplication; applications to fashion.

Niven, Chapters 1 and 2

Wednesday, September 19: How to count without counting II

Factorials; permutations; combinations; counting bridge hands, poker hands and pizzas.

Niven, Chapters 1 and 2

Friday, September 21: Probability

The notion of probability; combinatorial examples; mathematical interpretations of coin problems, dice, card games.

Niven, Chapter 5

Monday, September 24: The binomial theorem

Binomial coefficients; the binomial theorem.

Niven, Chapters 2 and 3

Wednesday, September 26: Pascal's triangle

Patterns among binomial coefficients; Pascal's triangle.

Niven, Chapter 3

Friday, September 28: Catalan numbers

A recursive relation; an actual formula.

Gross-Harris, Catalan Numbers

Monday, October 1: The Euclidean algorithm

Divisibility; greatest common divisors; Euclid's algorithm.

Wednesday, October 3: Diophantine equations I

Linear diophantine equations (solving equations with whole numbers) and greatest common divisors.

Friday, October 5: Diophantine Equations II

Solutions to linear diophantine equations via the Euclidean algorithm.

Wednesday, October 10: Review

Friday, October 12: First midterm exam

Monday, October 15: Prime numbers

Prime and composite numbers; existence of infinitely many primes; sieve of Eratosthenes.

Reid, Chapter 3

Wednesday, October 17: Unique factorization

Statement of unique factorization; examples of non-unique factorization.

Reid, Chapter 1

Friday, October 19: The fundamental theorem of arithmetic

The prime divisibility property; proof of unique factorization in the integers.

Monday, October 22: Numbers and number systems

Archimedes: the sand reckoner; natural numbers; integers; rational numbers; real numbers.

Archimedes, The Sand Reckoner
Gross-Harris, Chapter 1

Wednesday, October 24: Modular arithmetic I

Arithmetic mod m; viewing the integers modulo m as a number system.

Lines, Chapter 7 (pp. 60--64)
Reid, Chapter 9
Gross-Harris, Chapters 2, 3

Friday, October 26: Modular arithmetic II

Reinterpreting solutions to linear diophantine equations; computing inverses.

Reid, Chapter 9
Gross-Harris, Chapter 4

Monday, October 29 : Fermat's little theorem I

Computing powers in modular arithmetics; statement of Fermat's little theorem.

Gross-Harris, Chapter 5 (pp. 53--63)

Wednesday, October 31: Fermat's little theorem II

Two proofs of Fermat's little theorem.

Lines, Chapter 7 (pp. 64-66)
Gross-Harris, Chapter 5 (pp. 63--67)

Friday, November 2: Computing powers modulo p

Computing ridiculously large powers of numbers modulo p.

Gross-Harris, Chapter 5 (pp. 67--71)

Monday, November 5: Computing roots modulo p

Existence of roots modulo p; computing roots modulo p.

Gross-Harris, Chapter 6

Wednesday, November 7: Euler's theorem

The Euler phi-function; statement and proof of Euler's theorem.

Gross-Harris, Chapter 7 (pp. 85--94)

Friday, November 9: Computing powers modulo m

More computations in modular arithmetics; computing inverses as powers.

Gross-Harris, Chapter 7 (pp. 94--98)

Wednesday, November 14: Review

Friday, November 16: Second midterm exam

Monday, November 19: Computing roots modulo m

Existence of roots modulo m; computing roots modulo m; square roots.

Gross-Harris, Chapter 7 (pp. 98--100)

Wednesday, November 21: How to build codes I

Types of codes; historical examples.

Reid, Chapter e (pp. 159--163)

Monday, November 26: How to build codes II

RSA codes; coding and decoding.

Lines, Chapter 9

Wednesday, November 28: Distribution of primes I

Factorizing numbers on a computer; the prime number theorem; prime deserts.

Reid, Chapter e

Friday, November 30: Distribution of primes II

Pseudoprimes; primality tests; how to find large primes.

Monday, December 3: Distribution of primes III

More primality tests; are there infinitely many Mersenne primes?

Hoffman, Chapter 3

Wednesday, December 5: Distribution of primes IV

Distribution of primes modulo m; primes modulo 4.

Hoffman, Chapter 3

Friday, December 7: Return to Fibonacci numbers

Size of Fibonacci numbers; closed form expressions; Fibonacci numbers modulo m.

Lines, Chapter 2

Monday, December 10: Surprise Lecture

Wednesday, December 12: Review