It can be written: ジャン
ジャン /jan/ if you mean it as a name. If you mean 'January' it is 一月 /i chi ga tsu/. The word 'January' itself can be referred to in Japanese as ジャニュアリー /ja nyu a ri/.
Japanese artist and print maker is called Katsushika Hokusai.
cat paw print
"Jan" is the polish name for "John".
Jan Bielicz's birth name is Jan Toltyzewski.
Jan Skene's birth name is Jan Anderes.
Jan Seybold's birth name is Jan Niebuhr.
Jan Vrijman's birth name is Jan Hulsebos.
Jan Kounen's birth name is Coenen, Jan.
Jan Maervoet's birth name is Jan I Maervoet.
Jan Falk's birth name is Jan Lampkins.
Jan Ainley's birth name is Jan Porter.