This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A331113 #9 Jan 30 2020 22:02:36 %S A331113 1,1,9,96,1439,24758,476056,9841611,214997756,4900190330,115530636036, %T A331113 2800145556058,69446136484047,1756114394736162,45152546920446518, %U A331113 1177790435393100588,31111743336031473800,831007304851753985293,22416683345590695488558,610057933331757664054671 %N A331113 Number of signed trees with n positive edges and n negative edges. %C A331113 The total number of nodes is 2n + 1. Trees are unrooted. %H A331113 Andrew Howroyd, <a href="/A331113/b331113.txt">Table of n, a(n) for n = 0..100</a> %F A331113 a(n) = A302939(2*n + 1, n). %Y A331113 Cf. A302939, A331114. %K A331113 nonn %O A331113 0,3 %A A331113 _Andrew Howroyd_, Jan 09 2020