A remark on continued fractions for permutations and D-permutations with a weight $-1$ per cycle

Abstract

We show that very simple continued fractions can be obtained for the ordinary generating functions enumerating permutations or D-permutations with a large number of independent statistics, when each cycle is given a weight $-1$. The proof is based on a simple lemma relating the number of cycles modulo 2 to the numbers of fixed points, cycle peaks (or cycle valleys), and crossings.

LaTeX2e, 25 pages, includes 4 figures. Version 2 (34 pages, 6 figures) contains a slightly expanded introduction and a pair of running examples; to appear in the Electronic Journal of Combinatorics. arXiv admin note: text overlap with arXiv:2304.06545, arXiv:2212.07232, arXiv:2003.08192