Wilf classification of three and four letter signed patterns
نویسندگان
چکیده
We give some new Wilf equivalences for signed patterns which allow the complete classification of signed patterns of lengths three and four. The problem is considered for pattern avoidance by general as well as involutive signed permutations.
منابع مشابه
Restricted Single or Double Signed Patterns
Let E n = {[τ ]a = (τ (a1) 1 , . . . , τ (an) n )|τ ∈ Sn, 1 ≤ ai ≤ r} be the set of all signed permutations on the symbols 1, 2, . . . , n with signs 1, 2, . . . , r. We prove, for every 2-letter signed pattern [τ ]a, that the number of [τ ]a-avoiding signed permutations in E n is given by the formula n ∑ j=0 j!(r−1) ( n j 2 . Also we prove that there are only one Wilf class for r = 1, four Wil...
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عنوان ژورنال:
- Discrete Mathematics
دوره 308 شماره
صفحات -
تاریخ انتشار 2008