This article is from the Go FAQ, by Morten PAHLE gofaq@pahle.org.uk with numerous contributions by others.
Go is always a struggle of territory against central influence.
Territory is most often built on the third line from the edge, whereas
central influence most often arises from stones on the fourth line.
The 19x19 board is the one where the balance between third line
territory and fourth line influence is best. Refer to the following
diagram for explanation of this fact. (The low white position in the
corner is due to the necessity of having as many black as white stones
on the board.)
+-------------------------------------+ |. . . . . . . . . . . . . . . . . . .| |. . O O . . . . . . . . . . . O O . .| |. O # # O O O O O O O O O O O # # O .| |. O # # # # # # # # # # # # # # # O .| |. . O # . . . . . . . . . . . # O . .| |. . O # . . . . . . . . . . . # O . .| |. . O # . . . . . . . . . . . # O . .| |. . O # . . . . . . . . . . . # O . .| |. . O # . . . . . . . . . . . # O . .| |. . O # . . . . . + . . . . . # O . .| |. . O # . . . . . . . . . . . # O . .| |. . O # . . . . . . . . . . . # O . .| |. . O # . . . . . . . . . . . # O . .| |. . O # . . . . . . . . . . . # O . .| |. . O # . . . . . . . . . . . # O . .| |. O # # # # # # # # # # # # # # # O .| |. O # # O O O O O O O O O O O # # O .| |. . O O . . . . . . . . . . . O O . .| |. . . . . . . . . . . . . . . . . . .| +-------------------------------------+
 
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