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%I #13 Feb 25 2016 17:17:37
%S 5,489,321689,1840058693,93332304864173,41945191530093646965,
%T 166931297609667912727898521,5882748866432370655674372752123193,
%U 1835738613899845421140262364853644706891109,5072588588647327658457862518216696854885169490987149
%N Number of legal positions in Go played on an n X n+1 grid (each group must have at least one liberty).
%C Upper bounded by 3^{n*(n+1)}.
%H John Tromp, <a href="/A268113/b268113.txt">Table of n, a(n) for n = 1..19</a>
%H John Tromp, <a href="http://tromp.github.io/go/legal.html">Number of legal Go positions</a>
%H J. Tromp and G. Farnebäck, <a href="http://dx.doi.org/10.1007/978-3-540-75538-8_8">Combinatorics of Go</a>, Lecture Notes in Computer Science, 4630, 84-99, 2007.
%e For n=1 the 5 legal 1x2 boards are .. X. O. .X .O
%Y Almost-square version of A094777.
%K nonn,hard
%O 1,1
%A _John Tromp_, Jan 26 2016
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