Does divorce occur upon saying "You are divorced, divorced" to a wife who is pure and has not yet menstruated days after intercourse, and if it does occur, how many divorces are considered to have taken place?

The majority of scholars hold that divorce during menstruation or during a period of purity in which sexual intercourse occurred is valid, despite its being an innovation (bid'ah). Therefore, your divorce has occurred.

As for whether one or two divorces have occurred, this depends on your intention regarding the repetition: If you intended two divorces, then according to the majority of scholars, two have occurred. If you intended one divorce and repeated it for emphasis, or if you did not intend anything specific, then it is one, unless you intended to issue multiple divorces.

If this divorce does not complete the three (talaqs), then you may take your wife back before her 'iddah (waiting period) expires.