Fredrik Johansson, Brian Nakamura,
"Using functional equations to enumerate 1324-avoiding permutations"
, Serie arxiv, Nummer 1309.7117, RISC, Hagenberg, 2013
Using functional equations to enumerate 1324-avoiding permutations
Sprache des Titels:
We consider the problem of enumerating permutations with exactly r occurrences of the pattern 1324 and derive functional equations for this general case as well as for the pattern avoidance (r=0) case. The functional equations lead to a new algorithm for enumerating length n permutations that avoid 1324. This approach is used to enumerate the 1324-avoiders up to n=31. We also extend those functional equations to account for the number of inversions and derive analogous algorithms.