|標題：Signed countings of types B and D permutations and t,q-Euler numbers|
|作品名稱||Signed countings of types B and D permutations and t,q-Euler numbers|
|著者||Sen-Peng Eu; Tung-Shan Fu; Hsiang-Chun Hsu; Hsin-Chieh Liao|
|著錄名稱、卷期、頁數||Advances in Applied Mathematics 97, p.1-26|
|摘要||It is a classical result that the parity-balance of the number of weak excedances of all permutations (derangements, respectively) of length n is the Euler number , alternating in sign, if n is odd (even, respectively). Josuat-Vergès obtained a q-analog of the results respecting the number of crossings of a permutation. One of the goals in this paper is to extend the results to the permutations (derangements, respectively) of types B and D, on the basis of the joint distribution in statistics excedances, crossings and the number of negative entries obtained by Corteel, Josuat-Vergès and Kim.
Springer numbers are analogous Euler numbers that count the alternating permutations of type B, called snakes. Josuat-Vergès derived bivariate polynomials and as generalized Euler numbers via successive q-derivatives and multiplications by t on polynomials in t. The other goal in this paper is to give a combinatorial interpretation of and as the enumerators of the snakes with restrictions.
|關鍵字||Euler number;Springer number;Signed permutations;Derangements;Continued fractions;Weighted bicolored Motzkin paths|