منابع مشابه
Counting acyclic digraphs by sources and sinks
We count labeled acyclic digraphs according to the number sources, sinks, and edges. 1. Counting acyclic digraphs by sources. Let An(t;α) = ∑ D αt, where the sum is over all acyclic digraphs D on the vertex set [n] = {1, 2, . . . , n}, e(D) is the number of edges of D, and s(D) is the number of sources of D; that is, the number of vertices of D of indegree 0. Let An(t) = An(t; 1). To find a rec...
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ژورنال
عنوان ژورنال: Nature
سال: 2008
ISSN: 0028-0836,1476-4687
DOI: 10.1038/451026a