How many games available on PSP were released in 2004?
PSP refers to platform_name = 'PSP'; released in 2004 refers to release_year = 2004;
SELECT COUNT(T3.game_id) FROM platform AS T1 INNER JOIN game_platform AS T2 ON T1.id = T2.platform_id INNER JOIN game_publisher AS T3 ON T2.game_publisher_id = T3.id WHERE T1.platform_name = 'PSP' AND T2.release_year = 2004