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A304070 Number of simple graphs with n vertices rooted at a pair of distinguished vertices. 5

%I #12 May 07 2018 09:53:56

%S 0,2,8,40,240,1992,24416,483040,16343872,982635280,106979975168,

%T 21285548190080,7783083940331520,5254164116114948480,

%U 6577258363669088914432,15332656940815954900371968,66830735142688170751257497600,546722015615195079134707942219904

%N Number of simple graphs with n vertices rooted at a pair of distinguished vertices.

%C The graphs do not need to be connected.

%H Andrew Howroyd, <a href="/A304070/b304070.txt">Table of n, a(n) for n = 1..50</a>

%F a(n) = 2*A304069(n).

%e a(3)=8: 1 for the graph with no edge, 3 for the graph with one edge, 3 for the graph with two edges, 1 for the triangle.

%Y Cf. A304074 (for connected graphs), A000088 (not rooted).

%K nonn

%O 1,2

%A _Brendan McKay_, May 05 2018

%E Terms a(13) and beyond from _Andrew Howroyd_, May 06 2018

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Last modified March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)