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A134799 a(n)=3^((3^n - 1)/2). 0

%I #4 Apr 19 2016 01:07:36

%S 1,3,81,1594323,12157665459056928801

%N a(n)=3^((3^n - 1)/2).

%C Number of partitions into "bus routes" of the graph G_{n+1} defined below.

%H Author?, <a href="http://image.myany.jp/org/6c511f3698cf6db33d63d6450f331344.jpg">Mitsumata tree</a>

%e .........|..................G_1

%e ****

%e .......__|__................G_2

%e .........|

%e ****

%e .__|_____|_____|__..........G_3

%e ...|.....|.....|

%e .........|

%e .......__|__

%e .........|

%e ****.

%e ..._|_........._|_..........G_4

%e _|__|_____|_____|__|_

%e .|._|_....|...._|_.|

%e ....|.....|.....|

%e ......_|__|__|_

%e .......|._|_.|

%e ..........|

%e ****

%e G_1 = o---. = rooted tree with one edge and one leaf node. For n > 0, G_{n+1} is obtained from G_n by splitting each leaf node into three.

%Y Cf. A131709

%K nonn,easy

%O 0,2

%A _Yasutoshi Kohmoto_, Jan 09 2008

%E Edited by _N. J. A. Sloane_, Jan 29 2008

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)