Search: id:A089243
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%I A089243
%S A089243 0,1,3,4,9,22,55
%N A089243 Number of partitions into strokes of the edges of a star graph with n 
               edges.
%C A089243 Two arrangements are considered the same if one is a rotation or reflection 
               of the other.
%C A089243 A "stroke" is defined as follows. If the following conditions are satisfied 
               then the partition to directed paths on a directed graph is called 
               "a partition to strokes on a directed graph". And all directed paths 
               in the partition are called "strokes". C.1. Two different directed 
               paths in a partition do not have the same edges. C.2. A union of 
               two different paths in a partition does not become a directed path. 
               In other word, a "stroke" is a locally maximal path on a directed 
               graph.
%C A089243 This sequence has its origin in the strokes made when writing Japanese 
               Kanji.
%e A089243 n=3: this the Y graph. Call the center node "0" and the terminal nodes 
               "1", "2", "3". Four partitions exist as follows:
%e A089243 {1->0->2, 0->3}
%e A089243 {1->0->2, 3->0}
%e A089243 {1->0, 2->0, 3->0}
%e A089243 {0->1, 0->2, 0->3}
%e A089243 So a(3)=4.
%Y A089243 Sequence in context: A116868 A049976 A032789 this_sequence A034921 A038222 
               A038629
%Y A089243 Adjacent sequences: A089240 A089241 A089242 this_sequence A089244 A089245 
               A089246
%K A089243 nonn
%O A089243 1,3
%A A089243 Yasutoshi Kohmoto (zbi74583(AT)boat.zero.ad.jp)

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