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.
Note that talks are listed in reverse chronological order.
Date: February 13, 2026
Speakers: Jeff Rushall (NAU)
Abstract: About 22 centuries ago, Archimedes challenged a bunch of librarians (Eratosthenes was allegedly one of them) to solve a counting problem involving cows. The problem was sort of complicated and involved ENORMOUS numbers. I’ll present the history of the problem and explain how it was solved, and by whom.
The faculty guest this week is Ryn Huesgen. [PDF of Flyer]
Date: February 6, 2026
Speakers: Jeff Rushall (NAU)
Abstract: The title refers to a claim made by some physicists that the infinite sum 1 + 2 + 3 + 4 + … actually converges to a negative number. I’ll explain why they might be right, one painful step at a time.
The faculty guest this week is Bianca Luedeker. [PDF of Flyer]
Date: January 30, 2026
Speakers: Seb Pardo and Elenor Rushall (NAU)
Abstract: Any permutation of $\{1,2, \ldots, n\}$ may be written in one-line notation as a sequence of entries representing the result of applying the permutation to the identity $12\cdots n$. If $p$ and $q$ are two permutations, then $p$ is said to contain $q$ as a pattern if some subsequence of the entries of $p$ has the same relative order as all of the entries of $q$. If $p$ does not contain a pattern $q$, then $p$ is said to avoid $q$. One of the first notable results in the field of permutation patterns was obtained by MacMahon in 1915 when he proved that the ubiquitous Catalan numbers count the 123-avoiding permutations. We study pattern avoidance in the context of signed Cayley permutations. Introduced by Mor and Fraenkel in 1983, a Cayley permutation is a finite sequence of positive integers that include at least one copy of each integer between one and its maximum value. In a signed Cayley permutation, each entry can be positive or negative. In this talk, we explore pattern avoidance in signed Cayley permutations with the aim of providing species, exponential generating series, and counting formulas. We also include several conjectures and open problems.
The faculty guest this week is Natalie Pleuger. [PDF of Flyer]
Date: January 23, 2026
Speakers: Gabby Stewart (NAU)
Abstract: Graph pebbling is a game played on graphs; most known results are associated with undirected graphs. Gabby has been investigating the following question in an undergrad research project: are there any directed graphs whose single vertex cover pebbling numbers are constant? If you want to know what all of this means, and if you want to see her new results, come to FAMUS on Friday! No prior knowledge of graph theory or graph pebbling is expected.
The faculty guest this week is Nellie Gopaul. [PDF of Flyer]