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A008907 Number of legal tic-tac-toe (or noughts and crosses) positions after n plays, up to rotation and reflection. 3
1, 3, 12, 38, 108, 174, 204, 153, 57, 15 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

As in chess, a "play" is an action by a single player, a "move" is two contiguous plays by each opponent.

LINKS

Table of n, a(n) for n=0..9.

Index entries for sequences related to tic-tac-toe

EXAMPLE

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 --- --- --- --- --- ---

CROSSREFS

Sequence in context: A290930 A264423 A240193 * A048246 A217093 A278639

Adjacent sequences:  A008904 A008905 A008906 * A008908 A008909 A008910

KEYWORD

nonn,fini,full

AUTHOR

Russ Cox

EXTENSIONS

Additional comments from David W. Wilson, Jun 03 2001

STATUS

approved

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Last modified September 20 16:14 EDT 2017. Contains 292276 sequences.