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A268113 Number of legal positions in Go played on an n X n+1 grid (each group must have at least one liberty). 1
5, 489, 321689, 1840058693, 93332304864173, 41945191530093646965, 166931297609667912727898521, 5882748866432370655674372752123193, 1835738613899845421140262364853644706891109, 5072588588647327658457862518216696854885169490987149 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

LINKS

John Tromp, Table of n, a(n) for n = 1..19

John Tromp, Number of legal Go positions

J. Tromp and G. Farneb├Ąck, Combinatorics of Go, Lecture Notes in Computer Science, 4630, 84-99, 2007.

EXAMPLE

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

CROSSREFS

Almost-square version of A094777.

Sequence in context: A206502 A198249 A160363 * A152513 A012822 A124358

Adjacent sequences:  A268110 A268111 A268112 * A268114 A268115 A268116

KEYWORD

nonn,hard

AUTHOR

John Tromp, Jan 26 2016

STATUS

approved

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Last modified March 25 22:28 EDT 2019. Contains 321477 sequences. (Running on oeis4.)