Enumerating Alternating Trees
نویسندگان
چکیده
In this paper we examine the enumeration of alternating trees. We give a bijective proof of the fact that the number of alternating unrooted trees with n vertices is given by 1 n2 n?1 P n k=1 ? n k k n?1 , a problem rst posed by Postnikov in 4]. We also prove, using formal arguments, that the number of alternating plane trees with n vertices is 2(n ? 1) n?1 .
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ورودعنوان ژورنال:
- J. Comb. Theory, Ser. A
دوره 94 شماره
صفحات -
تاریخ انتشار 2001