activity
20062026
most citedThe enumeration of permutations avoiding 2143 and 4231

14 citations · 78 across the 33 of their papers we have counts for

collaborators

42 papers

math.CO2026

Shuffle automata and the growth of 1324-avoiding permutations

Robert Brignall

We show that . This is achieved by combining the approach of Bevan, Brignall, Elvey Price and Pantone using the `domino', with ideas from…

math.CO2026

Chains and unique transitive orientations of prime graphs

Robert Brignall, Sean Mandrick, Vincent Vatter

We give a short, conceptual proof that prime graphs have at most two transitive orientations, a much-quoted result of Gallai. Our proof uses chains, introduced by Chudnovsky, Kim,…

math.CO2026

Hereditary pattern-free classes are not always 2-wqo

Robert Brignall

A pattern is a fundamental object used in the proof of Duron, Mählmann and Toruńczyk to show that hereditary 2-wqo graph classes have bounded clique-width. We answer a question in…

math.CO2026

Linear clique-width and modular decomposition

Robert Brignall, Michal Opler, Vincent Vatter

A hereditary class of graphs has bounded clique-width if and only if its prime members do, but this lifting property fails for linear clique-width. We prove that a hereditary class…

math.CO2024

Pin classes II: Small pin classes

Robert Brignall, Ben Jarvis

Pin permutations play an important role in the structural study of permutation classes, most notably in relation to simple permutations and well-quasi-ordering, and in enumerative…

math.CO2024

On cycles in monotone grid classes of permutations

David Bevan, Robert Brignall, Nik Ruškuc

We undertake a detailed investigation into the structure of permutations in monotone grid classes whose row-column graphs do not contain components with more than one cycle. Centra…