%I #5 Sep 06 2017 11:27:30
%S 1,0,0,6,570,73620,13675620,3540401760,1229855690952,554518177819200,
%T 315663337023994080,221736991132524890880,188570961922698640977120,
%U 191056359142016559185938944,227491517759156008014967128000
%N Number of unordered pairs of edge-disjoint trees on n labeled vertices.
%H J. W. Moon, <a href="https://doi.org/10.1112/S0025579300004290">The second moment of the complexity of a graph</a>, Mathematika 11:2 (1964), 95-98.
%F For n>1, a(n) = A291952(n)/2.
%Y Cf. A291952.
%K nonn
%O 1,4
%A _Max Alekseyev_, Sep 06 2017