Enumeration of 3- and 4-Wilf classes of four 4-letter patterns
Enumeration of 3- and 4-Wilf classes of four 4-letter patterns is a scholarly work by Toufik Mansour, published in 2018 in ''Notes on number theory and discrete mathematics''. The main subjects of the publication include combinatorics, mathematics, automata theory, and enumeration. Let be the symmetric group of all permutations of letters.We show that there are precisely 27 (respectively, 15) Wilf classes consisting of exactly 3 (respectively, 4) symmetry classes of subsets of four 4-letter patterns.