A268113 Number of legal positions in Go played on an n X n+1 grid (each group must have at least one liberty).

5, 489, 321689, 1840058693, 93332304864173, 41945191530093646965, 166931297609667912727898521, 5882748866432370655674372752123193, 1835738613899845421140262364853644706891109, 5072588588647327658457862518216696854885169490987149

Offset: 1

Author

John Tromp, Jan 26 2016

Keywords

• nonn
• hard

Comments

Upper bounded by 3^{n*(n+1)}.

Examples

			For n=1 the 5 legal 1x2 boards are .. X. O. .X .O
		

Links

• John Tromp, Table of n, a(n) for n = 1..19
• John Tromp, Number of legal Go positions
• J. Tromp and G. Farnebäck, Combinatorics of Go, Lecture Notes in Computer Science, 4630, 84-99, 2007.

Crossrefs

Almost-square version of A094777.