|
%I #27 Sep 23 2019 02:02:11
%S 0,1,3,16,98,879,11260,230505,7949596,483572280,53011686200,
%T 10589943940654,3880959679322754,2623201177625659987,
%U 3286005731275218388682,7663042204550840483139108,33407704152242477510352455230,273327599183687887638526170380380
%N Birooted graphs: number of unlabeled connected graphs with n nodes rooted at 2 indistinguishable roots.
%H Andrew Howroyd, <a href="/A303831/b303831.txt">Table of n, a(n) for n = 1..40</a>
%H Jean-François Alcover, <a href="/A303831/a303831.txt">Mathematica program</a>
%F G.f.: B(x)/G(x) - (C(x^2) + C(x)^2)/2 where B(x) is the g.f. of A303829, G(x) is the g.f. of A000088 and C(x) is the g.f. of A126100. - _Andrew Howroyd_, May 03 2018
%F a(n) = A303830(n) + A304071(n). - _Brendan McKay_, May 05 2018
%t (* See the links section. *)
%Y Cf. A303829 (not necessarily connected). 3rd column of A304311.
%Y Cf. A000088 (not rooted), A126100 (connected single root), A053506 (2 roots adjacent).
%K nonn
%O 1,3
%A _Brendan McKay_, May 01 2018
%E a(12)-a(18) from _Andrew Howroyd_, May 03 2018
| 