Springer Numbers and Arnold Families Revisited
Abstract
For the calculation of Springer numbers (of root systems) of type and , Arnold introduced a signed analogue of alternating permutations, called -snakes, and derived recurrence relations for enumerating the -snakes starting with . The results are presented in the form of double triangular arrays () of integers, . An Arnold family is a sequence of sets of such objects as -snakes that are counted by . As a refinement of Arnold's result, we give analogous arrays of polynomials, defined by recurrence, for the calculation of the polynomials associated with successive derivatives of and , established by Hoffman. Moreover, we provide some new Arnold families of combinatorial objects that realize the polynomial arrays, which are signed variants of Andr\'{e} permutations and Simsun permutations.
Keywords
Cite
@article{arxiv.2111.00888,
title = {Springer Numbers and Arnold Families Revisited},
author = {Sen-Peng Eu and Tung-Shan Fu},
journal= {arXiv preprint arXiv:2111.00888},
year = {2021}
}
Comments
24 pages