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A008907
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Number of legal tic-tac-toe (or noughts and crosses) positions after n plays, up to rotation and reflection.
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6
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OFFSET
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0,2
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COMMENTS
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As in chess, a "play" is an action by a single player, a "move" is two contiguous plays by each opponent.
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LINKS
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EXAMPLE
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Example: a(2) = 12 since after 2 plays there are 12 legal positions:
-x- -x- -x- -x- -o- x-- x-- x-- x-o xo- o-- ox-
--- --- -o- o-- -x- --- --o -o- --- --- -x- ---
-o- o-- --- --- --- --o --- --- --- --- --- ---
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CROSSREFS
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KEYWORD
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nonn,fini,full
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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