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A008907 Number of legal tic-tac-toe (or noughts and crosses) positions after n plays, up to rotation and reflection. 6
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
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: A240193 A319077 A368097 * A048246 A320203 A217093
KEYWORD
nonn,fini,full
AUTHOR
EXTENSIONS
Additional comments from David W. Wilson, Jun 03 2001
STATUS
approved

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Last modified March 28 11:59 EDT 2024. Contains 371254 sequences. (Running on oeis4.)