Normally, go is played on a 19x19 board.
However, other sizes occur sporadically,
and especially 9x9 is somewhat popular.
(Statistics: one can maybe collect 100000 pro games on 19x19
and perhaps 1000 Japanese pro games on 9x9. This site has
40000+ 19x19 games, and 400+ 9x9 games played by Japanese pros.)
A long weekly series of 9x9 games came from the weekly
Yomiuri TV broadcast known as Minigo
For Rico Pairgo
there is an intermediate round played on 9x9.
(Two rounds are played. The pairs who lost twice are out.
The pairs who won twice can continue. The pairs who won once
and lost once play an intermediate knockout round on 9x9.)
This yields 28 games for 2003-2009.
Some NHK special events
are played on 9x9.
Miscellaneous 9x9 events.
In 2014 a Pro 13x13 Tournament
In 2016 a ProAma 13x13 Tournament
Four 2015 Kansai Ki-in 13x13
In 1964 a 15x15 game
Otake Hideo vs. Rin Kaiho was played.
In 1975 a 21x21 game
Hashimoto Shoji vs. Rin Kaiho was played.