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Number of unordered pairs of edge-disjoint trees on n labeled vertices.
1

%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