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%I #9 Jan 30 2020 22:02:36
%S 1,1,9,96,1439,24758,476056,9841611,214997756,4900190330,115530636036,
%T 2800145556058,69446136484047,1756114394736162,45152546920446518,
%U 1177790435393100588,31111743336031473800,831007304851753985293,22416683345590695488558,610057933331757664054671
%N Number of signed trees with n positive edges and n negative edges.
%C The total number of nodes is 2n + 1. Trees are unrooted.
%H Andrew Howroyd, <a href="/A331113/b331113.txt">Table of n, a(n) for n = 0..100</a>
%F a(n) = A302939(2*n + 1, n).
%Y Cf. A302939, A331114.
%K nonn
%O 0,3
%A _Andrew Howroyd_, Jan 09 2020