{ "id": "1909.05887", "version": "v1", "published": "2019-09-12T18:04:43.000Z", "updated": "2019-09-12T18:04:43.000Z", "title": "Exceptional Sequences and Idempotent Functions", "authors": [ "Emre Sen" ], "comment": "Comments are welcome!", "categories": [ "math.RT" ], "abstract": "We prove that there is one to one correspondence between the following three: idempotent functions on the set of size $n$, exceptional sequences of linear radical square zero Nakayama algebras of rank $n$ and rooted labeled forests with $n$ nodes and height of at most one. Therefore, the number of exceptional sequences is given by the sum $\\sum\\limits^n_{j=1}\\binom{n}{j}j^{n-j}$.", "revisions": [ { "version": "v1", "updated": "2019-09-12T18:04:43.000Z" } ], "analyses": { "subjects": [ "16G20", "05E10", "05C30" ], "keywords": [ "exceptional sequences", "idempotent functions", "linear radical square zero nakayama", "radical square zero nakayama algebras" ], "note": { "typesetting": "TeX", "pages": 0, "language": "en", "license": "arXiv", "status": "editable" } } }