Mathematics & Statistics Seminars
Northern Arizona University


The “Friday Afternoon Mathematics Undergraduate Seminar” (FAMUS) is a weekly event consisting of announcements, talks, and faculty interviews. FAMUS takes place most Fridays at 3:00-4:00pm in Room 164 of the Adel Mathematics Building. Typically the first half of FAMUS consists of a talk on a mathematical topic while an interview of a faculty member takes place in the second half. FAMUS is hosted by Jeff Rushall.

Come join us for some entertaining talks! Refreshments always served.

Schedule Spring 2020

Note that talks are listed in reverse chronological order.

Friedman Numbers

Date: Friday, March 6

Speaker: Jeff Rushall (NAU)

Abstract: Friedman numbers are positive integers that can be formed by combining the digits of the integer using any of addition, subtraction, multiplication, division and exponentiation. For instance, 25 and 688 are Friedman numbers because 25 = 5^2 and 688 = 86x8. In the presentation I will show interesting examples of Friedman numbers, and discuss the various variations of Friedman numbers (via adding more operations, or insisting on non-repeating digits, or searching for PRIME Friedman numbers, etc.). The processes involved border on numerology, but they are certainly entertaining. A flyer is attached for your perusal.

The faculty guest is John Neuberger. [PDF of Flyer]

The Moving Sofa Problem

Date: Friday, February 28

Speaker: Jeff Rushall (NAU)

Abstract: In the presentation I will explain the titular problem: what is the largest “sofa” that can be moved around a 90-degree corner (with no tilting or twisting allowed)? This is essentially the 2-D version of the classic “ladder problem” from calc I. It turns out that this 2-D version is not so easy to solve.

The faculty guest is Gina Nabors. [PDF of Flyer]

The Happy Ending Problem

Date: Friday, February 21

Speaker: Jeff Rushall (NAU)

Abstract: In the presentation I will tell a tale that SHOULD be better known. It features the four key ingredients for any good story: math, love, tragedy, and Paul Erdos. The math is a simple geometry problem that remains unsolved. The love, tragedy and Erdos connections? Come and find out!

The faculty guest is Shannon Guerrero. [PDF of Flyer]

The Platonic Solids et al.

Date: Friday, February 14

Speaker: Jeff Rushall (NAU)

Abstract: In the presentation I will explain a humorous puzzle created by David Hilbert, who died on “Valentine’s Day” in 1943. The puzzle deals with the following: if a normal/finite hotel is full, there are no vacancies. But if we are talking about an infinite hotel, well, even if the hotel is full, it isn’t full. The consequences are fun. Amusing pictures will be shown.

The faculty guests are David Deville and Sarah Watson, rather appropriate for Valentine’s Day, eh? [PDF of Flyer]

The Platonic Solids et al.

Date: Friday, February 7

Speaker: Jeff Rushall (NAU)

Abstract: In the presentation I will define the Platonic solids, mention their development historically, explain (with hand waving) why there are only 5 such solids, and discuss variations (Johnson solids, Archimedean solids, etc.). Amusing pictures will be shown. [PDF of Flyer]

Pentagonal Planar Tilings

Date: Friday, January 31

Speaker: Jeff Rushall (NAU)

Abstract: Inspired by Dr. Blows’ recent colloquium on this topic, I will give a similar presentation, describing the history of the problem of finding all monohedral pentagonal planar tilings.

The faculty guest will be Derek Sonderegger. [PDF of Flyer]

Sylver Coinage Digraphs

Date: Friday, January 24

Speaker: Chloe Frechette (NAU)

Abstract: In the talk, we will explain the game of Sylver Coinage, how the game translates nicely into a graph theory context, and the progress we have made analyzing families of graphs in terms of finding winning strategies in Sylver Coinage. This talk is “practice” for my poster presentation at the Nebraska Conference for Undergraduate Women in Mathematics.

The faculty guest will be Ian Williams. [PDF of Flyer]