Formula 17 (17歲的天空, pinyin: shí qī suì de tiān kōng) is a 2004 film which was directed by Chen Yin-jung (陳映蓉). It stars Tony Yang (楊佑寧), Duncan (周群達), King Chin (金勤), Dada Ji (季宏全), Jimmy Yang (楊俊明), and Jason Chang (張大鏞). It is a gay romantic comedy film about Chou T'ien-Tsai, a romantic Taiwanese male who takes a trip to visit an online boyfriend in person for the first time. Finding his internet relationship unsuitable for his real life, he moves on with his life and rooms with an old time friend of his. The film describes T'ien's experiences with his loyal roommate and his friends, and a surprising relationship that he develops with the local "Playboy".

This film was banned in Singapore because it "portrayed homosexuality as normal, and a natural progression of society".

Naive countryman Chou T'ien-Tsai goes to Taipei to meet an internet friend face-to-face. Being a romantic, and believing in 'true love' (he even has a book called Love Is A Kind Of Faith), he is sorely disappointed when his friend suggests they have sex with no love. T'ien instead goes to a bar and runs into his ex-classmate Yu and in the process meets the 'Number One Playboy' Bai Tie Nan, who is notorious for one night stands. T'ien very quickly develops a liking towards Bai.